Download - Form 5 Matter and Atomic)
8/6/2019 Form 5 Matter and Atomic)
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Atomic Structure
8/6/2019 Form 5 Matter and Atomic)
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John Dalton (1807)
• British Schoolteacher
–based his theory on
others’ experimental data
• Solid Sphere Model
–atom is a
uniform,solid sphere
8/6/2019 Form 5 Matter and Atomic)
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John Dalton
Dalton’s Four Postulates
1. Elements are composed of smallindivisible particles called atoms.
2. Atoms of the same element are
identical. Atoms of differentelements are different.
8/6/2019 Form 5 Matter and Atomic)
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3. Compounds contain atoms of
more than one element
4. In a compound, atoms of different
elements always combine the same
way.
8/6/2019 Form 5 Matter and Atomic)
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J. J. Thomson (1903)
• Cathode Ray TubeExperiments
–beam of negative
particles
• Discovered Electrons
–negative particles within
the atom
• Plum-pudding Model
8/6/2019 Form 5 Matter and Atomic)
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J. J. Thomson (1903)
Plum-pudding Model
–positive sphere(pudding) with
negative electrons
(plums) dispersed
throughout
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Ernest Rutherford (1911)
• Gold Foil Experiment
• Discovered the nucleus –dense, positive
charge in the center of
the atom• Nuclear Model
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Ernest Rutherford (1911)
• Nuclear Model
–dense, positive nucleus surrounded by negative
electrons
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James Chadwick (1932)
Discovered the neutron
– neutral particleswithin the atom
8/6/2019 Form 5 Matter and Atomic)
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Subatomic Particles
P O S I
C H A R
P R O T O
N E U T
C H A R
N E U T R O
N U C L E
N E G A T I V E
E L E C T R
A T O M
NUCLEUS ELECTRONS
PROTONS NEUTRONS NEGATIVE CHARGE
POSITIVECHARGE
NEUTRALCHARGE
ATOM
8/6/2019 Form 5 Matter and Atomic)
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Proton, electron and
neutron
8/6/2019 Form 5 Matter and Atomic)
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Subatomic Particles
P O S IC H A R
P R O T O
N E U TC H A R
N E U T R O
N U C L E
N E G A T I V E
E L E C T R
A T O M
Most of the atom’s mass. Number
equals the # of...
in a neutral atom
NUCLEUS ELECTRONS
PROTONS NEUTRONS NEGATIVE CHARGE
POSITIVECHARGE
NEUTRALCHARGE
ATOM
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Atomic Structure
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How do we compute for the number
of protons, electrons and neutrons
in a neutral atom?
8/6/2019 Form 5 Matter and Atomic)
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• Proton Number
= Number of Proton
• Nucleon Number
= Number of proton +
number of neutron
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Example
Determine :
C126
Proton Number =
Nucleon Number =Number of
proton = 6, electron = 6
neutron = Nucleon-proton
= 12-6
= 6
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Ions
• Charged particle
• Positive ion
proton more than electron
• Negative ion
proton less than electron
• Neutral (no charge)proton = electron
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Isotopes
• Atoms that have the same number of
protons but different numbers of
neutrons.
Ex. 11H – hydrogen
2
1
H – deuterium
31H – tritium