Atomic Structure
• John Dalton 1808 (a chemistry &
• Greek - 5th century concept of atoms physics teacher)
• Leucippus –intuition that matter
contain tiny particles that could be - 19th century that greatly
subdivided.
• Democritus (460-370) BC experimenting, gathering facts,
- Develops the idea of atoms and evidences w/c led to the
- Proposed that matter composed formulation of the atomic
of tiny indivisible & indestructible theory.
particles, Atomos. He pounded up - Suggested that all matter was
materials in his pestle and made up of tiny spheres that
mortar until he had reduced were able to bounce around
them to much smaller particles., with perfect elasticity and called
he called; Atoma; Greek for them, atoms.
indivisible.
- He believed each atom is distinct
& that substance is mixture of
different atom that can break
down small until cannot be
divided anymore (individual
atom).
- However, his work was based
hypothetically mental
experienced/reasoning w/c lack
experiment to reveal truth.
• Aristotle - Declared that matter could - Dalton's Model of the Atom
be subdivided indefinitely, however * Atom has no nucleus
he rejected existence of atom. A view *Atom is solid and indivisible
which prevailed for 2000 years.
• Francis Bacon- (1561-1626) revived
concept of atom w/c he called - All elements are made up of tiny, indivisible
Corpuscula w/c means primary particles called Atoms.
particle of matter. -All atoms of a given element (size, shape and
other properties) are chemically alike, Atoms
of different elements are chemically different
- Compounds are composed of two or more
elements; in ratio of the number of atoms of
,any two elements present in a compound is The number of substances may change, the
fixed & can be expressed in simple whole no. properties may change, but the total
amount of matter remains constant.
In any chemical reaction, atoms of one
element are not changed into atoms of The next slide illustrates the Law of
another element but combine to form Conservation of Mass and third hypothesis
different substances; a chemical reaction of Dalton.
does not result in the creation or
Example:
destructions of atoms.
1. 5 g of solid butter melts to 5 g of liquid
Theory 1: Discovery of subatomic particles
butter
led to an alteration of first theory. Existence
2. 63.5 g of Copper + 16.00 g of Oxygen =
of subatomic particles proves atom are still
79.5 g of Copper Oxide
divisible.
3. 79.5 g material before change = 79.5 g
Theory 2: atoms of same element are after change
identical in mass was found to be defective 4. 50 g H2O when heated to evaporate
when isotopes were discovered. produce 30 g of H2 ↑and 20 g O2 ↑
Theory 3: restatement of law proposed by What is the Law of Definite
Joseph Proust stated that. Law of definite Composition by Joseph Proust?
composition- relative numbers & kinds of
A law that states that elements combine
atoms in a compound is constant.
to form compound. They do so in definite
Theory 4: Law of Conservation of matter- proportions (fractions) by mass.
fundamental law of chemical combination
The fraction is obtained by dividing the
led development of Dalton theory. Law
mass of the element by the total mass of
proposed by Lavoisier stated matter is
the compound.
neither created nor destroyed in chemical
reaction. Total mass of substances before & The percent by mass (Mass percent or
after reaction remains the same. mass %) is the mass fraction expressed
as percentage
What is the Law of Conservation of Mass
by John Dalton?
It states that the total mass in any
chemical or physical change does not
change.
, Consider the substance water H2O have an Example:
analysis of 18 g
Exactly 16.00 g of oxygen reacts completely
2g of Hydrogen and 16 g of oxygen with 7.00 g of nitrogen.
% H = 2/ 18 x100 = 11% How many grams of oxygen will react with
3.00 g nitrogen?
% O = 16/ 18 x 100 = 89%
Show the reaction between O and N conform
100%
with the law of conservation of mass
What law John Dalton discovered during
What other law is illustrated in the problem?
formulating the theory?
a) 3 g N x 16.00 g O = 6.86 g O
Law of Multiple Proportions – law states
7.0 N
that a given quantity of an element may
b) From the given information
combine with different quantities of another
element to form different compounds. 16.0 0 g O +7.00 g N = 23 g NO
Water & Hydrogen peroxide:2 different From the solution (a)
compound w/ same element combining
6.86 O + 3.00 N =9.86 g NO
whose ratios of atoms are different. H2O 2: 1
c) Law of definite composition
ratio H2O2 = 2: 2 ratios
How electrons were discovered using
What is the Law of Multiple Proportion by
Cathode Rays.
John Dalton?
through his experiment
This law states that if two elements combine
used a device, cathode ray tube in
(A and B) to form different compounds, the
discovering electrons.
masses of one element (B) that combined a
with affixed mass of another (A) can be A cathode ray tube has two metal electrode
expressed as a ration of small whole such as & connected to vacuum that removes gas
1:2, 2:3, 3:4 and so on. from tube. He passed an electric current
thru the tube & observed a glowing beam of
Carbon monoxide (CO) and carbon dioxide
rays originating from cathode (- electrode)
(CO2) are such examples, The ratio of the
traveled in straight path to the anode (+
masses of oxygen that combine with given
electrode).
mass of carbon is 1:2 CO is 1:1 ratio CO2 is 1:
2 ratios He called the beam cathode rays because it
come from cathode.
Similar may be cited with SO2 and SO3, H2O
and H2O2 and CH4 and C2H4. This law makes The glow is created when electric current
use of the first, 2nd and fourth postulates. SO2 strikes the remaining gas. The beam travels
is 1:2, while SO3 is 1:3 ratio; CH4 is 1:4 ratio & in straight path in the absence of external
C2H4 is 2:4 or 1:2 ratio applied electric field.
• John Dalton 1808 (a chemistry &
• Greek - 5th century concept of atoms physics teacher)
• Leucippus –intuition that matter
contain tiny particles that could be - 19th century that greatly
subdivided.
• Democritus (460-370) BC experimenting, gathering facts,
- Develops the idea of atoms and evidences w/c led to the
- Proposed that matter composed formulation of the atomic
of tiny indivisible & indestructible theory.
particles, Atomos. He pounded up - Suggested that all matter was
materials in his pestle and made up of tiny spheres that
mortar until he had reduced were able to bounce around
them to much smaller particles., with perfect elasticity and called
he called; Atoma; Greek for them, atoms.
indivisible.
- He believed each atom is distinct
& that substance is mixture of
different atom that can break
down small until cannot be
divided anymore (individual
atom).
- However, his work was based
hypothetically mental
experienced/reasoning w/c lack
experiment to reveal truth.
• Aristotle - Declared that matter could - Dalton's Model of the Atom
be subdivided indefinitely, however * Atom has no nucleus
he rejected existence of atom. A view *Atom is solid and indivisible
which prevailed for 2000 years.
• Francis Bacon- (1561-1626) revived
concept of atom w/c he called - All elements are made up of tiny, indivisible
Corpuscula w/c means primary particles called Atoms.
particle of matter. -All atoms of a given element (size, shape and
other properties) are chemically alike, Atoms
of different elements are chemically different
- Compounds are composed of two or more
elements; in ratio of the number of atoms of
,any two elements present in a compound is The number of substances may change, the
fixed & can be expressed in simple whole no. properties may change, but the total
amount of matter remains constant.
In any chemical reaction, atoms of one
element are not changed into atoms of The next slide illustrates the Law of
another element but combine to form Conservation of Mass and third hypothesis
different substances; a chemical reaction of Dalton.
does not result in the creation or
Example:
destructions of atoms.
1. 5 g of solid butter melts to 5 g of liquid
Theory 1: Discovery of subatomic particles
butter
led to an alteration of first theory. Existence
2. 63.5 g of Copper + 16.00 g of Oxygen =
of subatomic particles proves atom are still
79.5 g of Copper Oxide
divisible.
3. 79.5 g material before change = 79.5 g
Theory 2: atoms of same element are after change
identical in mass was found to be defective 4. 50 g H2O when heated to evaporate
when isotopes were discovered. produce 30 g of H2 ↑and 20 g O2 ↑
Theory 3: restatement of law proposed by What is the Law of Definite
Joseph Proust stated that. Law of definite Composition by Joseph Proust?
composition- relative numbers & kinds of
A law that states that elements combine
atoms in a compound is constant.
to form compound. They do so in definite
Theory 4: Law of Conservation of matter- proportions (fractions) by mass.
fundamental law of chemical combination
The fraction is obtained by dividing the
led development of Dalton theory. Law
mass of the element by the total mass of
proposed by Lavoisier stated matter is
the compound.
neither created nor destroyed in chemical
reaction. Total mass of substances before & The percent by mass (Mass percent or
after reaction remains the same. mass %) is the mass fraction expressed
as percentage
What is the Law of Conservation of Mass
by John Dalton?
It states that the total mass in any
chemical or physical change does not
change.
, Consider the substance water H2O have an Example:
analysis of 18 g
Exactly 16.00 g of oxygen reacts completely
2g of Hydrogen and 16 g of oxygen with 7.00 g of nitrogen.
% H = 2/ 18 x100 = 11% How many grams of oxygen will react with
3.00 g nitrogen?
% O = 16/ 18 x 100 = 89%
Show the reaction between O and N conform
100%
with the law of conservation of mass
What law John Dalton discovered during
What other law is illustrated in the problem?
formulating the theory?
a) 3 g N x 16.00 g O = 6.86 g O
Law of Multiple Proportions – law states
7.0 N
that a given quantity of an element may
b) From the given information
combine with different quantities of another
element to form different compounds. 16.0 0 g O +7.00 g N = 23 g NO
Water & Hydrogen peroxide:2 different From the solution (a)
compound w/ same element combining
6.86 O + 3.00 N =9.86 g NO
whose ratios of atoms are different. H2O 2: 1
c) Law of definite composition
ratio H2O2 = 2: 2 ratios
How electrons were discovered using
What is the Law of Multiple Proportion by
Cathode Rays.
John Dalton?
through his experiment
This law states that if two elements combine
used a device, cathode ray tube in
(A and B) to form different compounds, the
discovering electrons.
masses of one element (B) that combined a
with affixed mass of another (A) can be A cathode ray tube has two metal electrode
expressed as a ration of small whole such as & connected to vacuum that removes gas
1:2, 2:3, 3:4 and so on. from tube. He passed an electric current
thru the tube & observed a glowing beam of
Carbon monoxide (CO) and carbon dioxide
rays originating from cathode (- electrode)
(CO2) are such examples, The ratio of the
traveled in straight path to the anode (+
masses of oxygen that combine with given
electrode).
mass of carbon is 1:2 CO is 1:1 ratio CO2 is 1:
2 ratios He called the beam cathode rays because it
come from cathode.
Similar may be cited with SO2 and SO3, H2O
and H2O2 and CH4 and C2H4. This law makes The glow is created when electric current
use of the first, 2nd and fourth postulates. SO2 strikes the remaining gas. The beam travels
is 1:2, while SO3 is 1:3 ratio; CH4 is 1:4 ratio & in straight path in the absence of external
C2H4 is 2:4 or 1:2 ratio applied electric field.
