General Chemistry

1 S T S E M E S T E R P R E L I M I N A R YE X A M I N A T I O N R E V I E W E R

CHAPTER 1: Matter and Its Properties

LESSON 1: Properties of Matter and Methods of Separation
What are the properties of matter?
⤹ Just before the pandemic (COVID-19), we are experiencing right now, have you ever looked into a
crowd of people during SM Mall sales and instantly recognized a former schoolmate in your elementary or
junior high school days? You learn to recognize people by the shape of their face, the color of their hair and
eyes, the way the walk, and many other physical characteristics. Their distinct characteristics make them easy
to identify even in a crowd. A sample of matter can be identified in a similar way- by observing its
characteristics, or properties.
⋆ Physical Properties ⋆
⤹ It is the characteristics of a substance that can be observed without altering the identity of the
substance.
⤹ Examples of physical properties includes:
⸙mass ⸙meltingpoint
⸙texture ⸙boilingpoint
⸙color ⸙freezingpoint
⸙odor ⸙solubility
⸙phase(solid,liquid,andgas) ⸙density
⸙temperature ⸙volatility-howeasilyasubstancecanvaporize
⸙volume ⸙viscosity-resistanceoffluidtochangesubstance
⸙shape ⸙conductivity
⤹ For example, you are given a piece of gold nugget. How are you going to describe the characteristics of gold
nugget? Definitely, you are going to describe it as a yellow, solid, hard substance. What are the physical properties
used to describe the gold nugget? Can you enumerate them?
⤹ Pure water has the following characteristics: colorless, tasteless, boils at 100oC, freezes at 0oC, has a density of
approximately 1 g/mL, and dissolve many substances. What are the physical properties of water-based on the cited
characteristics?
⤹ WATER is a universal solvent.
⋆ Chemical Properties ⋆
⤹ It is the characteristics of a substance that cannot be observed without altering the substance
⤹ Examples of chemical properties includes:
⸙ flammability
⸙ toxicity
⸙ reactivity
⸙ heat of combustion

What are the Methods of Separating Components of a Mixture?

༄Paper Chromatography
⤹ It is the technique used to separate small amounts of substances from a mixture based on the different
solubilities of the components in the particular solvent
 ⤹ A chromatography technique used to separate mixture of chemical substances into its individual
compounds
⤹ ⤹ADVANTAGE 1: Only a small sample is required for the analysis
2: It can also be used as a method to determine if the sample is pure
⤹ Paper chromatography consists of two phases:
⸙ one mobile phase
moved along
⸙ one with a compound
contiguous stationarymixture
phase through the paper according to the polarity and the degree of adhesion
of each component on the stationary phase. is made of cellulose. A suitable solvent (mobile phase) is
The paper used in paper chromatography

⤹ The ratio of the distance that the compound traveled and the distance that the solvent traveled is
�����R��f.distan�ce��tr�a�v�e�l�le�d�b�y�t�hℎe�s�o�lu�t�ef
denoted as
⤹ R =
���STEPBYSTEPPROCEDURE(Basedonthevideo):
STEP 1: Using a filter paper, draw a start line about 1.5 cm from the base using a pencil
STEP2: Apply small but concentrated spots of the sample on the piece of chromatography paper
NOTE: This is important as it is to ensure that there are enough sample to ensure that there are
enough sample as the individual components will be diluted when they move along the paper
: If the sample spots are too large, it will be difficult to distinguish the individual spots on the
chromatogram. The spots should be made as small as possible to prevent tailing as well as smudging
when the inks or dyes are separated
STEP 3: Add a small amount of suitable solvent to the beaker
NOTE: The choice of solvent depends on the type of sample we are using, in the experiment, since
it used a water-based ink, water is a suitable solvent since the inks are soluble in water
STEP 4: Place the chromatography paper and immerse it in the solvent
NOTE: Do not forget to cover the beaker with a lid since it minimizes the evaporation of the
solvent as it travels up the paper
: It also ensures that the atmosphere in the beaker is saturated with solvent vapour which stops the
solvent from evaporating as it rises up the paper
⤹ You will now notice that the solvent moves up the chromatography paper and it carries the different dyes
with it. Dyes which are more soluble in the solvent will migrate faster and further
STEP 5: When the solvent front has reached near the top, remove the chromatogram and mark the
solvent front with a pencil line
SOLVENT FRONT: The highest height that the solvent has reached. It should be marked as soon as
the paper is removed from the solvent as it starts to fade when removed from the solvent. It must run
ashighaspossiblebeforeremovingthepaper, the further it is from the start line, the better the
separation for the spot of the dye for accurate identification. However, it should not overrun, otherwise
the actual distance it covered cannot be measured or determined
: Knowing the solvent front is important for the calculation of the Rf values
 Photo 1 Photo 2
On Photo 1:
⤹ ⤹Having
⤹ just one dye, we can say that the ink is pure
up the paperink in the video is a mixture of 3 dyes, whereas the blue dye is the most soluble solvent
The black
The purple dye in the video is insoluble in water as it remained at the start line and did not migrate

⤹ ⤹For the dyes that were not well separated, you can try to change the solvent
upUsing a pencilwhich
of graphite to draw the start line,
is insoluble willsolvent
in the lead to an accurate chromatogram since a pencil line is made
On Photo 2:

⤹ Using a pen/marker for the start line, it will also move up on the paper or dissolve in the solvent, so
then it will lead to complicate the results
On Photo 3:
⤹ If the ink spots are below the solvent level, the inks don’t
get carried up the peper, but instead dissolve in the solvent

Photo 3

Decantation Steam Distillation

༄Decantation
⤹ This separation technique separates an insoluble solid from a liquid.
⤹ The process of pouring away liquid while leaving a solid (often a sediment) behind
༄Steam Distillation
⤹ This separation technique purifies a liquid mixture by using the boiling points of its substances.
 ⤹ A method of separating mixture based on differences in their volatilities in a boiling liquid mixture.
The components in a sample are vaporized by the application of heat and then immediately cooled by
the
⤹ Itaction of coldtowater
also allows in a condenser
separate compounds that are immiscible with the distillation liquid

(usually water). used to separate essential oils from plants and other source.
⤹ It is commonly
STEP BY STEP PROCEDURE (Based on the video):
STEP 1: Extract the lemon oil by grating the peel using a grater. It is a tiring process so you must
remain patient. Brush of the grater to get the maximum amount of lemon peels.
Put
STEPthe2:grated peel into a flat-bottomed flask using a funnel.
Add water
STEP 3: to the flask, half way full.
Then assemble
STEP 4: the distillation apparatus.
NOTE: Remember to connect the refrigerator in order to let bubbles escape when they reach the
highest part of the refrigerator.
: Also connect the water lines in order to let water flow in the opposite direction to vapors.

Refrigeratorpointedbywhitearrow Waterlinesareadded
: Complete the circuit by eliminating air bubbles
: It is not necessary to place a thermometer but, however, it was shown how to
place it in the adapter using a cutted rubber bulb from pipettes
: Modify its height until the bulb is not higher than the right arm of the
distilling head
STEP 5: Add a stir bar to the flask that contains the mixture and put it on the hot
stirrer
STEP 6: Place a receiving flask
STEP 7: Connect the heat and the stirring
NOTE: It is important to give it a good stir to avoid overheating
STEP 8: It will begin to boil after a few minutes.
NOTE: You may now start to notice how vapor climbs up through the system. These vapor contains the
compounds the lemon has. The oil is co-distilled with the help of water and then, as it
is immiscible with it, it forms two phases that is why it would appear as a cloudy liquid in the
condenser
: The vapor would then start to condense and the first drops of distillate may appear.
: The oily drops in the distillate means that the oil is being extracted properly.
STEP 9: After an hour and half, check if there is still oil by taking a drop of distillate and see if it still
contains oily drops
NOTE: If the distillate still has oil, continue extracting the oil for about another hour.
STEP 10: Turn off the stirring and the heat, and then remove the heater to help stop the distillation.
⤹ Extraction comes now, and a liquid-liquid extraction will be done using hexane as the solvent
STEP 11: Place the separatory funnel in the stand and make sure the stopcock is closed.
 STEP 12: Pour the extraction liquid carefully and wash the flask with water for a few times and still add
it in the separatory funnel.
STEP 13: Add 10ml of hexane to the funnel and place the stopper.
STEP14: Shaketheseparatoryfunneltoreleasethepressurethatmayforminthefunnelconstantly.
After that let it stand for a few seconds.
STEP 15: Open the stopcock and drain the aqueous phase into the Erlenmeyer flask.
STEP 16: Close the stopcock when organic phase reaches it and recover it in a separated container.
STEP 17: Repeat the process (Steps 11-16), but this time just using 5ml of hexane
STEP 18: Boil the hexane to isolate the oil.
STEP 19: When about 10ml was left, pour the liquid into the final container, and wash the beaker with
2ml of hexane.
NOTE: Continue the evaporation of hexane in the final container in low heat.
: Place the thermometer on the container to see if there is hexane left

Evaporation Filtration
༄Evaporation
⤹ This separation technique separates a mixture by allowing the liquid to evaporate and the solid
particles will remain in the evaporating dish
⤹ Water will evaporate and the solid will remain by the aid of heat
Mixture of salt and water
⤹
Filtration
༄
⤹ This technique separates an undissolved solid from a liquid using filter paper.
⤹ Technically defined as the process of separating suspended solid matter from a liquid, by causing
the latter to pass through the pores of a membrane, called a filter paper.
⤹ It is better than decantation to separate heterogeneous mixtures
Mixture of powdered chalk and water
⤹

Sublimation Crystallization
༄Sublimation
⤹ This separation technique is applicable for separating a liquid mixture. As you heat the liquid, it
evaporates and the solid crystals will start to form as sublimate.
⤹ Transition of a substance directly from the solid phase to gas without passing through the
intermediate liquid phase
⤹ Solid directly to gas
༄Crystallization
⤹ This separation technique is similar to sublimation. The impure solid is dissolved in a solvent. The
solution is heated and evaporation takes place. The hot solution is allowed to cool and crystals will
gradually form.
⤹ Defined as a process by which a chemical is converted from a liquid solution into a solid crystalline

state

Electrolysis Magnetism Separatory Funnel

༄Electrolysis
⤹ This technique is used to separate compounds like water. Two test tubes are filled with acidified
water and connected to a 6 volt battery. Electrodes are inserted inside the test tubes. The hydrogen ions
are attracted to the cathode while the oxygen ions are attracted to the anode.
Process by which ionic substances are decomposed (broken down) into simpler substances when an
༄Magnetism / Magnetic Separation
⤹ It is used to separate a mixture of a metal in a mixture
It is the process of separating components of mixture by using magnets to attract magnetic materials
⤹ Mixture of nails and sand
⤹
༄Separatory Funnel
⤹ It is used to separate two immiscible liquids like oil and water.
Also known as separation funnel, separating funnel, is a piece of laboratory glassware used in
⤹
liquid-liquid extractions to separate the components of a mixture into two immiscible solvent phases
of different densities
⤹
Mixture of cooking oil and water
LESSON 2: Pure Substances and Mixtures in Common Consumer Products
What is a Chemical Formula?
⤹ Chemical formula shows the elements present and the number of atoms of each element in the
compound.
CommonName ChemicalName ChemicalFormula
Water DihydrogenMonoxide H2O
TableSugar Sucrose C12H22O11
TableSalt SodiumChloride NaCl
BakingSoda SodiumBicarbonate NaHCO3
Sodium hydrogen
Carbonate
AceticAcid EthanoicAcid CH3COOH
CreamofTartar PotassiumHydrogen KC4H5O6
VitaminC Tartrate C6H8O6
MuriaticAcid AscorbicAcid HCl
Bleach HydrochloricAcid CaOCl2
CalciumHypochlorite

W h⤹atisaConsumerProduct?Aconsumerproductisanyitemoftenboughtforconsumption.Consumerproductsaremadeupof

different components that differentiate their properties and uses them from other products.
⤹ A convenience product is a type of consumer product that is usually present in large amounts in the
market because of its demand in everyday life. Two examples of convenience products is household cleaning
products and personal care products.
༄ Household Cleaning Materials
⤹ When the pandemic, (COVID-10), explode like a bomb, the demand in household cleaning
products increases. These cleaning products became essential needs in any household,
establishments (schools, offices, industry) for health care purposes.
⤹ Chemicals present in household cleaning products, like soap, laundry detergent, bleaches,
dishwashing liquids, and other household cleaners, help improve safety, cleaner and more
hygienic environment.
༄ Personal Care Products
⤹ Consumers often use the term "personal care products" to refer to a wide variety of items that
we commonly find in the health and beauty sections of drug and department stores.
⤹ Some of the products commonly referred to as "personal care products" are cosmetics. These
include, for example, skin moisturizers, perfumes, lipsticks, fingernail polishes, eye and facial
makeup preparations, shampoos, permanent waves, hair colors, toothpaste, and deodorants.
Some, however, are regulated as drugs. Among these are skin protectants (such as lip balms and
diaper ointments), mouthwashes marketed with therapeutic claims, antiperspirants, and
treatments for dandruff or acne.
⤹ Some "personal care products" meet the definitions of both cosmetics and drugs. This may
happen when a product has two intended uses. For example, a shampoo is a cosmetic because
its intended use is to cleanse the hair. An antidandruff treatment is a drug because its intended
use is to treat dandruff. Consequently, an antidandruff shampoo is both a cosmetic and a drug,
because it is intended to cleanse the hair and treat dandruff. Among other cosmetic/drug
combinations is a toothpaste that contains fluoride, deodorants that are also antiperspirants,
and moisturizers and makeup marketed with sun-protection claims. Such products must comply
with the requirements for both cosmetics and drugs.
⋆ Uses and Benefits ⋆
⤹ Chemicals in cleaning products like laundry detergent can help these products to perform just as well in
cold water as in hot water, enabling consumers to save money and energy when washing their clothes. In addition,
highly concentrated liquid laundry formulations made possible by chemistry require less packaging materials and
generate less waste.
⤹ Household cleaning products containing antibacterial cleaners not only remove dirt and soil, but they
also can kill the germs that may cause illness.
⤹ Chlorinated cleaning products can help protect against seasonal flu outbreaks and episodes of
foodborne illness. Daycare centers, hospitals, restaurants, and other public facilities rely upon the disinfectant
qualities of chlorine-based cleaners to keep the environment germ-free.
⤹ Cleaning solvents are also common cleaning products. For example, glycol ethers are highly effective
as an active component of heavy-duty glass, floor, and other hard surface cleaning formulations. These
solvents have good water compatibility, high solvency for greases and oils and good biodegradability
⋆ Safety Information ⋆
⤹ Companies are providing more information than ever about ingredients in their cleaning products. The
Consumer Product Ingredient Communication Initiative, launched in 2010, summarizes how companies are
providing information about the ingredients in products in four major categories: air care, automotive care, cleaning,
and polishes and floor maintenance products
⤹ Cleaning products, while safe and effective, must be handled appropriately to protect the health of
consumers and their families. Users should follow all safe handling instructions on a product’s label before
using a particular cleaning product.
⤹ The Federal Hazardous Substances Act (FHSA) requires precautionary labeling on containers of any
consumer product that poses a likelihood of injury, to help consumers safely store and use those products and
to provide information about immediate first aid steps to take if an accident happens
⤹ The counterpart of FHSA in the Philippines is the Food and Drug Administration (FDA) whose main
function is to establish safety or efficacy standards and quality measures for foods, drugs, and devices and
cosmetics and other health products.

CHAPTER 2: Atomic Structure

LESSON 1: Atoms and Isotopes
What is an atom?
⤹ They are the basic units of matter and the defining structure of elements. The term atom comes from the
Greek word “atomos” which means indivisible, because it was once thought that atoms were the smallest things in
the universe and could not be divided. We now know that atoms are made up of three particles: protons, neutrons
and electrons.
⤹ The smallest particle of a chemical element that retains its chemical properties.
An atom is the defining structure of an element, which cannot be broken by any chemical means. A
⤹
typical atom consists of a nucleus of positively charged protons and electrically neutral neutrons with negatively
charged electrons orbiting this nucleus. However, an atom can consist of a single proton (i.e., the protium isotope of
hydrogen) as a nucleus. The number of protons defines the identity of an atom or its element.
What are the subatomic particles of an atom?

⸙ Electrons (e-)
⤹ The smallest subatomic component of an atom and are very light.
Electronscarrya negative charge atalltimes.Theyexistwithinorbital
clouds of an atom. An electromagnetic force keeps the electron from leaving the atom’s orbit. The electron
 orbits the atom so fast it is almost impossible to determine the exact location of an electron at a specific time.
They are the only subatomic particle that the atom can either give up or gain another one of during chemical
bonding. The negative charge of the electron balance out the positive charge of the proton, which helps to
establish an overall neutral charge for the atom. ⸙ Protons (p+)

⤹ Located within the nucleus of the atom, a proton has a relatively larger mass than that of an electron but
slightly smaller than that of a neutron. A proton will always have at least one positive charge (it is a positively
charged particle. The proton is responsible for the atom's atomic number. The positive proton charge balances
out the negative charge exhibited by the electrons. The protons share the nucleus of the atom with the
neutrons and whether free from or bound, the proton maintains a high degree of stability. The protons are
important in differentiating among different atoms because the number of protons of a particular atom is
specific to that atom. It also determines the chemical properties that the atom will have. ⸙ Neutron (n0)

⤹ Neutrons are also located in the atom's nucleus and get their name from their chemical charge, which is
neutral. The numbers of neutrons along with the protons in the atom give the overall mass number of the atom.
Much heavier than electrons and slightly bigger than protons, the number of neutrons within the nucleus of an
atom determines the number of isotopes that a particular atom can form. Neutrons are very stable in their
bound form within the atom; however, free neutrons are extremely unstable and undergo decay.

⤹ These 3 are always expressed in whole numbers.

What are the Characteristics of Subatomic Particles?
⤹ The characteristics of the 3 subatomic particles are tabulated for you

What is an atomic number, atomic mass and mass number?

⋆ Atomic Number (Z) ⋆
⤹ represented by Z, is the. number of protons in the nucleus of an atom.
⋆ Mass Number (A) ⋆
⤹ the total number of protons and neutrons inside the nucleus of an atom.
⋆ Atomic Mass ⋆
⤹ also known as atomic weight, is the average mass of atoms of an element, calculated using the relative
abundance of isotopes in a naturally occurring element.
⤹ If rounded off it will be the mass number
⸙ Example
⤹ REMEMBER:
In a neutral atom:
Z : number of protons =
number of electrons

A : number of protons +
number of neutrons

Number of neutrons = A ‒ Z
Net Charge Atom is always 0
It is neutral atom if it is not positively
or negatively charged.
What is an isotope?
⤹ Isotopes are atoms with the same number of protons but differing numbers of neutrons. In other words,
isotopes have different atomic mass. Isotopes are different forms of a single element.

⤹ In the case of the three isotopes of hydrogen, it has the same atomic number (1), number of protons
amd electrons (1), but the numbers of neutrons are different
༄ Calculating Atomic Weight and Isotopic Abundance

⤹ Let us determine the atomic weights and isotopic abundance of some isotopes.
Example 1: Neon has three isotopes with the following percentage abundances and isotopic masses:
⸙
90.51% 20Ne (19.992 amu); 0.27% 21Ne (20.993 amu) and 9.22% 22Ne (21.991 amu). Calculate the
atomic weight of Neon.
⤹ Most abundant is 20Ne

STEP 1: You convert the given percentageNe = 90.51% of=the

0.9051
20
abundance three isotopes of neon to decimals.
21
Ne = 0.27% = 0.0027
22
Ne = 9.22% = 0.0922
STEP 2: The values you obtained after converting percentage to decimals will be multiplied to their
respective isotopic masses. Add the relative masses to get the atomic weight of neon.
20Ne=0.9051x19.992amu= 18.0947592amu = 18.10
21
Ne=0.0027x20.993amu= 0.0566811amu
2.0275702amu==0.057 2.03
22
Ne=0.0922x21.991amu=
= 20.1790105amu = 20.187 = 20.19 amu
STEP 3: The calculated atomic weight of Neon is 20.1790105 amu which is rounded to 20.18 amu.
⤹ If the calculation used subtraction or addition, use the least amount of decimal places
10
 ⤹ If it uses multiplication or division, use the least significant figures
⸙ Example 2: Rubidium has two naturally occurring isotopes, 85Rb (isotopic mass, 84.9118amu) and 87Rb
(isotopic mass, 86.9092 amu). If rubidium has an average atomic mass of 85.47 amu, what is the percentage
abundance of each isotope of rubidium? Which is the most abundant isotope? STEP 1: Since the sum of the
percentage of any isotopes is 1 (100%), so the relative abundance of the isotopes can be found using simple
algebra.
Let: x = abundance of Rb 85

1‒ x = abundance of Rb 87

STEP 2: Use the equation below to solve for the abundance of 85Rb;
Isotopicmassof Rb(x)+isotopicmassof
85
Rb(1‒x)=atomicweight
87

STEP 3: Substitute the given values to solve for x.

84.9118amu(x)+86.9092amu(1‒X) =85.47amu
84.9118amux + 86.9092amu ‒ 86.9092amux = 85.47amu
84.9118amux‒86.9092amux =
=85.47amu‒86.9092amu‒1.9974amux=−−��‒..�

(cancel amu here)

STEP 4: Use the equation; 1 ‒ x, to calculate the abundance of 87Rb

1 ‒ 0.72054 = 0.27946
STEP 5: Multiply the values obtained with 100% to get the percentage abundance of 85Rb and 87Rb
85
%abundance Rb =0.72054x100%=72.054%
%abundance Rb 87
=0.27946x100%=27.946%
STEP 6: Identify the most abundant isotope.
⤹ Most abundant isotope is 85 Rb because it has a greater percentage abundance.
⤹ The sum of abundances of any isotope is always 1.
⤹ Base from the calculated percentage abundance of the two isotopes of rubidium, the most abundant isotope
is 85Rb because it has a greater percentage than 87Rb.
Common Isotopes and their Uses

Radioactive Isotopes Uses/Application

Americium-241 Used in smoke detector
Calcium-47 Important aid to biomedical researchers studying
cellular functions and bone formation in mammals
Carbon-11 Tagged onto glucose to monitor organs during a PET
scan
Carbon-14 Study metabolism changes for patients with diabetes,
gout, and anemia
Cesium-137 Used to treat cancerous tumors
To measure correct dosages of radioactive
pharnaceuticals
Chromium-51 Used in research in red blood cells survival studies
and determination of blood volume
Cobalt-57 Used as a tracer to diagnose pernicious anemia
Cobalt-60 Used to sterilize surgical instruments
Used in cancer treatment, food irradiation and
radiography
Copper-67 When injected to monoclonal antibodies into a cancer

11
 patient, helps the antibodies bind to and destroy the
tumor.
Gallium-67 Usedinmedicaldiagnosis
Hydrogen-3 Watercontentofthehumanbodyandarchaeological
Iodine-123 dating
Iodine-125 Widelyusedtodiagnosethyroiddisordersandother
metabolic disorders including brain functions.
Majordiagnostictoolusedinclinicaltestandto
diagnose thyroid disorders. Also used in biomedical
research.
Iodine-129 Iodine- Usedtochecksomeradioactivitycountersinin-vitro
131 Iridium-192 diagnostic testing laboratories
Iron-59 Phosphorus- Usedtotreatthyroiddisorders.(Graves’sdisease)
32and Phosphorus- Inbrachytherapy/tumorIrradiation
33 Radium-226 Diagnosisforanemiaandpregnancydisorder
Sodium-24 Thallium- Usedinmolecularbiologyandgeneticsresearch.
201 Technetium- Usedforthetreatmentofcancer
99m Locationofbloodclot,studybloodcirculationand
pumping action of the heart
Determinedamageinhearttissue,detectionoftumors
Mostwidelyusedradioactivepharmaceuticalfor
diagnostic studies in nuclear medicine. Different
chemical forms are used for brain, bone , liver, spleen
and kidney imaging
Usedindentalfixtureslikecrownsanddenturesto
provide a natural color and brightness.
Uranium-234
Usedasnuclearreactorsandweapons
Uranium-235
Usedinarchaeologicaldating
Uranium-238
Usedinnuclearmedicineforlungventilationand
Xenon-133
blood flow studies.

What is an ion?
⤹ It is defined as an atom or molecule that has gained or lost one or more of its valence electrons, giving
it a net positive or negative electrical charge. In other words, there is an imbalance in the number of protons
(positively charged particles) and electrons (negatively charged particles) in a chemical species.
⤹ Can either be a negative or positive charge
⋆ Comparison Between an Atom and an Ion⋆
⤹ REMEMBER:
In an ion:
Z = number of protons ≠ number of
electrons
A = number of protons + number of
neutrons
Number of neutrons = A ‒ Z

12
 ⤹ Sodium Atom (Na), Sodium Ion (Na+) is more stable because it has 8 valence electrons in its outer shell
⤹ Oxygen Atom (O), Oxygen Ion or Oxide (O-2) gained 2 ions in order for the outer shell to be stable
⤹ Look at your tabulated data, it shows that the atomic number (Z) is equal to the number of protons but
not equal to the number of electrons. Maybe you are wondering why the number of electrons is not the same as
atomic number. It’s because the sodium atom loses its one valence electron. If an atom loses one or more
electrons, then the atom becomes a positively charged ion which is known as cation. Otherwise, if an atom gains
one or more electrons like in the case of oxygen then the atom becomes a negatively charged ion which is known as
anion.
⤹ Stable atoms has 8 valence electrons
LESSON 2: Writing and Naming Chemical Formula
Chemical Formula
⤹ It is defined as a substance that expresses the kinds and number of atoms of each element in the
compound.
⤹ Here are some examples of chemical formula:
⸙ Let us take, for example, water, H2O, 1 molecule of water is composed of two atoms of hydrogen
and one atom of oxygen.
⸙ Another example is the table sugar, with a chemical formula of C12H22O11 and a chemical name of
sucrose. A molecule of sugar/sucrose is made of 12 atoms of carbon, 22 atoms of hydrogen and 11
atoms of oxygen.
⤹ When writing chemical formulas, the cation is always first and the anion are last.
⤹ Stable chemical formulas must be written so that the overall compound has a net neutral charge.
⤹ Subscripts are used to show how many atoms are present with ionic formula
⤹ In naming and writing chemical formulas, you should be familiar with the formula of the monoatomic
ions, polyatomic ions and even the Greek prefixes to correctly name and write the chemical formulas.
⤹ Listed on the next page is the formula that you need to be familiar with in order to correctly write and
name substances.

13
 ⋆ MonoatomicAnions⋆

⋆ PolyatomicAnions⋆
*The only polyatomic cation is NH4+, ammonium ion

14
 ⋆ Elements with Variable Valence Number⋆

⋆ Elements Occurring as Polyatomic Molecules⋆

⋆ Greek Prefixes ⋆
If it is a combination of non-metals, it is a covalent substance then you would use Greek Prefixes

Remove the last vowel on the Greek Prefixes if the element starts with a vowel

15
༄Writing Chemical Formula
⤹ Below are the guidelines you on how you are going to write chemical formula step by step.
⸙ Example 1: Lithium Fluoride
STEP 1: Write the symbol of the cation (positive ion) followed by the symbol of the anion (negative
ion). The cation ion and anion ion in lithium fluoride is Li+ and F‒ respectively.
STEP 2: The charges of the ions are omitted, since the sum of the charges is equal to zero.
Li+ Cl‒ Note:1+(‒I)=0
STEP 3: The number of each ion needed to make a neutral compound is indicated by a subscript written
after the symbol of the ion. Usually the subscript “1” is not written.
STEP 4: Write the formula for lithium fluoride, which is LiF.
⸙ Example 2: Magnesium Oxide
STEP 1: Write the symbol of the cation and anion in magnesium oxide.
Cation:Mg2+ Anion:O2‒
STEP 2: The charges of the ions are omitted, since the sum of the charges is equal to zero.
Mg2+ O2‒ Note:2+(‒2)=0
STEP 3: The number of each ion needed to make a neutral compound is indicated by a subscript
written after the symbol of the ion. Again the subscript “1” is not written.
STEP 4: Write the formula for magnesium oxide, which is MgO.
⸙ Example 3: Barium Phosphate
STEP 1: Write the symbol of the cation and anion in barium phosphate.
Cation:Ba2+ Anion:PO43‒
STEP 2: You need to apply the crisscross method, the valence number of cation will become the
subscript of the anion, and the valence number of the anion will be the subscript of the cation. Disregard
the +(positive) and ‒ (negative)sign of the cation and anion.
Ba2+ PO43‒
STEP 3: Enclosed in parenthesis the PO4, to separate the subscript 3.The chemical formula for
barium phosphate is Ba3(PO4)2.

⸙ Example 4: Ammonium Carbonate

STEP 1: Write the symbol of the cation and anion in ammonium phosphate.
Cation:NH4+ Anion:CO32‒
STEP 2: You need to apply the crisscross method, the valence number of cation will become the
subscript of the anion, and the valence number of the anion will be the subscript of the cation. Disregard
the +(positive) and ‒ (negative)sign of the cation and anion.
NH4+ CO32‒
STEP 3:Enclosed in parenthesis the NH4to separate the subscript 2. The chemical formula for
ammonium carbonate is (NH4)2CO3.

༄Naming Chemical Formula for Ionic Compounds

⤹ Innamingioniccompound,givethenameofthecationfirstfollowedbythenameoftheanion.
⸙Example1: Give the name of MgO.
STEP 1: Identify the cation and anion.
STEP 2: Cation:Mg 2+ Anion:O 2‒
Name the cation and anion.
Cation:Mg Magnesium
2+

16
 Anion:O2‒ Oxide
STEP 3: Name the ionic compound. The name of MgO is Magnesium Oxide.

⸙ Example2: GivethenameofFeO .
STEP 1: Identify the cation and anion.
STEP 2: Cation:Fe2+ Anion:O2‒
Name the cation and anion.
Cation: Fe2+ Iron(II) Stock name
Fe2+ Iron(II) Classical name
Anion: O2‒ Oxide
STEP 3: Name the ionic compound. The Stock name of the ionic compound is Iron(II)Oxide. The
Classicalnameofthecompoundis Ferrous Oxide .

༄Naming Inorganic Acids

⤹ Hydrogen is always written first
⸙ Example 1: Give the name of HCl(aq).
STEP 1: Since you have here an aqueous solution of HCl. Name the substance by adding the
prefix hydro and the suffix –ic to the root name of the nonmetal followed by the word acid.
Cl hydro+chlor+ic
Root name
Nonmetal
STEP2:Nametheacid. ThenameofHCl(aq)isHydrochloricAcid.

⸙ Example 2: Give the name of HCl.

⤹ Indryconditions,itisnamedashydrogenfollowedbythestemofthenonmetalandending with
the suffix –ide. The name of HCl is Hydrogen Chloride.

༄Naming Oxyacid
⤹ Give the name of the common acid.
⸙ Example: HClO3
ClO3‒ ischlorate,droptheending–ateandchangewith–ic+thewordacid
HClO3 ChloricAcid (commonacid)

⤹ Drop the ending –ate of the polyatomic anion and change with the suffix –ous.
The suffix –ous denotes an acid with one less oxygen atom than the common acid.
⸙ Example:HClO2 ChlorousAcid

⤹ The prefix per- with the suffix –ic denotes an acid with one or more oxygen atom than the common
acid.
⸙ Example: HClO4 Perchloric Acid

⤹ The prefix hypo- with the suffix –ous denotes an acid with two less oxygen atom than the common acid.
⸙ Example: HClO Hypochlorous Acid

༄Naming of Salts
⸙ Example 1: NaClO3
STEP 1: Name the metallic element first, followed by the name of the nonmetallic element.
17
 Metallic element: Sodium Nonmetallic element: Chlorate
STEP 2: Namethesalt.Thenameofthesaltis Sodium Chlorate .

༄Rules in Naming Molecular Covalent Compounds

⤹ If only one atom of an element is present in the molecule, the prefix mono is usually omitted.
⤹ The name of the first element in the formula is retained.
⤹ The name of the second element in the formula is modified by adding the suffix –ide.
⸙ Example: CO carbon monoxide
SCl2 sulfur dichloride

18