Holt 2 1
Holt 2 1
Holt 2 1
Life
Section 1: The Nature of
Matter
Objectives
SWBAT identify & describe the parts
of an atom IOT differentiate between
elements.
Atom
Basic unit of matter
Made of protons, neutrons,
electrons, and LOTS of
empty space
Subatomic particles
Bind
together
to form
the
nucleus
Protons:
Neutrons:
Electrons: Positively charged (+)
Not charged (neutral)
Protons
Negatively
charged
(-)
Electrons
Neutron
s
Nucleus
Element
A pure substance that
consists of just one type of
atom
Ex: gold, copper,
aluminum, chlorine,
hydrogen, helium, etc.
Carbon
12.011
Atomic
number = #
of protons
Carbon
12.011
Mass number
Isotope
Atoms of the same
element that have
different #s of neutrons.
All isotopes of a given
element have the SAME #
of protons.
radioactive carbon-12
6 electrons
6 protons
6 neutrons
Nonradioactive carbon-13
6 electrons
6 protons
7 neutrons
Radioactive carbon-14
6 electrons
6 protons
8 neutrons
Radioactive isotopes
Can be
dangerous
Can be used
practically
Radioactive
dating
Treat cancer
Kill bacteria
Table Salt
Types of ions:
Cation: an atom that loses
an electron; positive
charge
Anion: an atom that gains
an electron; negative
charge
Summary
An atom has electrons (negative charge) in orbit
around its nucleus. The nucleus is composed of
protons (positive charge) and neutrons
(neutral/no charge). Unless otherwise noted,
atoms have the same number of electrons and
protons, which means atoms have NO overall
charge.
Isotopes of an element all have the same # of
protons but different #s of neutrons.
Ions are atoms that gained or lost electrons and
have a negative or positive overall charge.
Octet Rule
Atoms prefer 8 electrons in their
valence (outer) shell
Compounds
A substance made when
atoms of two or more different
elements join together.
Represented by a chemical
formula that identifies the
elements in the compound
and their proportions.
Ex: H2O, NaCl, CO2
Covalent Bonds
Atoms share electrons to
satisfy the octet rule
This happens because the
atoms are trying to fill
their valence shells.
Molecule
A particle made up of two or
more atoms joined by a
covalent bond
Smallest unit of most
compounds
Ionic Bonds
Bonds between atoms that lose or gain
electrons.
Results in some atoms with positive
charge and others with negative charge
Atoms are held together because of the
attraction between opposite charges.
Ex: Sodium (Na) and chlorine (Cl) interact
and form an ionic bond to make table
salt, a.k.a. sodium chloride (Na+Cl-)
Protons +11
Electrons -10
Charge
+1
Protons +17
Electrons -18
Charge
-1
Transfer
of electron
Protons +11
Electrons -11
Charge
0
Protons +17
Electrons -17
Charge
0
Homework
Homework 2.1
1. Describe the structure of an atom.
2. Explain why all isotopes of an
element have the same chemical
properties.
3. What is a covalent bond?
4. What is an ionic bond?
5. What is a compound? How are
they related to molecules?
Bohr Models
Bohr models are used to predict
reactivity in elements.
2. Reactivity refers to how likely an
element is to form a compound with
another element.
3. When looking at Bohr models, we look at
its valence electrons (the electrons on
the last energy level) to determine
reactivity.
1.
Guided Practice
In order to draw Bohr models of these elements, you
must first determine the number of protons, neutrons,
and electrons. Once you have found this information,
follow the directions to draw your model.
6
C
Carbon
12.011
6
6
6
Protons: _____
Neutrons: _____
Electrons: ______
2
How many energy shells will this have? ____
4
How many valence (outer) electrons does this element have? ____
Bohr Model:
Guided Practice
3
Li
Lithium
6.941
3
4
3
Protons: _____
Neutrons: _____
Electrons: ______
2
How many energy shells will this have? ____
1
How many valence (outer) electrons does this element have? ____
Bohr Model:
Guided Practice
16
S
Sulfur
32.066
16
16
16
Protons: _____
Neutrons: _____
Electrons: ______
3
How many energy shells will this have? ____
6
How many valence (outer) electrons does this element have? ____
Bohr Model:
Guided Practice
11
Na
Sodium
22.990
11
12
11
Protons: _____
Neutrons: _____
Electrons: ______
3
How many energy shells will this have? ____
1
How many valence (outer) electrons does this element have? ____
Bohr Model:
Guided Practice
15
P
Phosphorus
30.974
15
16
15
Protons: _____
Neutrons: _____
Electrons: ______
3
How many energy shells will this have? ____
5
How many valence (outer) electrons does this element have? ____
Bohr Model: