Midterm Pharm. Inorganic Q#2

MIDTERM PHARM.
INORGANIC Q#2
John Dalton helped to revolutionize chemistry with his hypothesis that the behavior of matter could
be explained using an atomic theory. First published in 1807, many of Dalton’s hypotheses about the
microscopic features of matter are still valid in modern atomic theory.
HENCE, IN YOUR OWN UNDERSTANDING enumerate & explain each of the 5 postulates of Dalton’s
atomic theory.
The concept of ultimate particles, or atoms of matter, did not contribute to the development
of science until the beginning of the 19 th century. Between 1803 and 1807 in England, school teacher
John Dalton (1766-1844) performed many chemical experiments, particularly with gases. He greatly
extended man’s ideas about atoms.
Dalton was the first to realize that the nature and properties of atoms could be used to
explain the Law of Definite Compositions and the proportions in which substances react with one
another. These are the fundamental ideas of Dalton’s Atomic Theory.
The atomic theory today embraces a much wider field of knowledge than Dalton’s original
theory. The modern atomic theory includes information concerning structure and properties of
atoms, the kinds of reactions they undergo, the kinds of compounds they form and the properties of
these compounds. It also includes information about the mass, volume and energy relationships in
reactions between atoms.
An atom is the smallest particle of an element that can exist either alone or in combination
with other atoms of the same or of another element. The postulates of Dalton’s Atomic Theory are:
1.Matter is composed of exceedingly small particles called atoms. An atom is the smallest unit of
an element that can participate in a chemical change.
Matter is defined as anything that occupies space and has mass, whereas atoms are the
building blocks of matter. Atom is from the Greek word atomos meaning indivisible or uncuttable.
They are typically made up of main parts: proton having positive charge; electrons- having negative
charge; and neutrons which are neutral. Atoms are small, really small. We probably heard this during
our lecture from elem up to now that matter is made up of bundles of these tiny things. We can’t
see this particles with the naked eye. We are told to take the idea that atoms are there, interacting
with each other and being the building blocks for our world. These particles are so small that even
when you put them under the microscope, even the most powerful light-focusing microscope can’t
visualize single atom. What makes an object visible is the way it deflects visible light waves.
2.An element consists of only one type of atom, which has a mass that is characteristic of the
element and is the same for all atoms of that element. A macroscopic sample of an element
contains an incredibly large number of atoms, all of which have identical chemical properties.
When a substance contains only one type of atom, it is called element. Each element has a
special name and unique properties that are different from all the rest of the elements. We know
that elements are made of tiny bits of atoms. The fundamental characteristics that all of the same
element shares is, the number of protons. The number of protons is equal to the atomic number of
an element. In all electrically neutral atoms, the number of electrons is the same as the number of
protons. Thus, each element, at least when electrically neutral, has characteristic number of
electrons equal to its atomic number.
3. Atoms of one element differ in properties from atoms of all other elements.
All atoms are not the same, the number and arrangement of electrons in an atom define the
chemical characteristics of an element. Electrons are the part of atom located outside, they are the
outer coating. The number of electrons, protons, and neutrons makes atoms of one element
different from the other. The number of protons in an atom determines what element is that like for
instance, carbon has six proton and hydrogen has one proton. While the properties of an element
are decided by the number of electrons. Different elements have different number of electrons so
they differ from each other.
4.A compound consists of atoms of two or more elements combined in a small, whole-number
ratio. In a given compound, the numbers of atoms of each of its elements are always present in
the same ratio.
In relation to the postulate of the Atomic Theory of John Dalton stated above, John Dalton
formulated the Law of Multiple proportions also known as Dalton’s Law as part of his theory that
atoms formed the basic indivisible building block of matter. The law, which was based on Dalton’s
observations of the reactions of atmospheric gases, states that when elements form compounds can
be expressed in small whole number ratios. The law, is an extension of the law of definite
composition, which states that compounds will consist of defined ratios of elements.
5.Atoms are neither created nor destroyed during a chemical change, but are instead rearranged
to yield substances that are different from those present before the change.
John Dalton used three laws of chemical reactions as basis for his theory, one of this is the
Law of Conservation of Mass wherein it states that atoms are neither created nor destroyed during a
chemical change; the total mass of matter present when matter changes from one type to another
remain constant. And the process in which one or more substances, the reactants, are rearranged or
converted to yield one or more different substances or compound, the products, is called Chemical
Reaction. Chemical reaction rearranges the constituent atoms of the reactants to create different
substance. This connects to the occurrence of historical significance concerning chemical reactions
of the development of The Atomic Theory.

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