lect notes 4

Chem 1048A
BHSc
Learning Goal 4:
Atomic Structure
(Attendance at lectures is necessary to complete these notes)



Ms Brankin
Office 303
(011) 717-6729


, Atomic Structure
• 3 subatomic particles have a bearing on chemical
behaviour: proton, neutron and electron
– Charge of electron = -1.602 x 10-19C
– Charge of proton = +1.602 x 10-19C

• Electronic charge = 1.602 x 10-19C, with charges
usually expressed as multiples of this charge 
– Charge of electron = -1
– Charge of proton = +1
– Charge of neutron = 0 i.e. neutral

• Atoms are neutral because they have an equal
number of protons and electrons.

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, Atomic Structure
• The mass of a proton is 1.0073 amu, a neutron is
1.0087 amu, and an electron is 5.486 x 10–4 amu.
• Protons and neutrons are located in the nucleus of
the atom, which is small
– Most of the mass of the atom is due to the nucleus.
• Electrons are located outside of the nucleus
– Most of the volume of the atom is due to electrons.

1Å = 10-10 m




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, Atomic Number & Mass Number
Atomic number (Z) = no. of protons in the nucleus
Mass number (A) = total no. of nucleons in the nucleus
i.e. protons + neutrons

By convention, for element X, we write:
A
Z X
What makes one element different from another element?
All atoms of a specific element have the same number
of protons.

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