2. NUCLEUS OF AN ATOM
• Composition of the nucleus of an atom
in terms of protons and neutrons
• Proton number (Z) and nucleon number
(A)
• Nuclide notation
• Isotopes

3. Composition of the nucleus of an atom in terms
of protons and neutrons
Electrons
orbit the
nucleus
Nucleus
Contains
neutrons
and protons

4. Proton number (Z) and nucleon number (A)
Proton number is known as the number
of protons and labelled as Z
 Nucleon number is the total number of
protons and neutrons. It is symbolised
as A
 Number of neutrons is A-Z.
 Example,

A
12
C
6
Z

5. Example 1
1. Atom K has 4 protons and 3
neutrons. Calculate the
nucleon number of atom K.
Proton number=4
Number of neutrons=3
∴ nucleon number
= proton number + number of neutrons
=4+3=7

6. Example 2
2.
18
p
L
Given number of
neutrons is 7. Find p.
Nucleon number=18
Number of neutrons=7
∴ proton number
= nucleon number – number of neutrons
= 18 -7 = 11

7. Example 3
3. Atom Z consists of 36 nucleons
and 17 protons. Calculate the
neutrons of atom Z.
Nucleon number = 36
Protons number = 17
∴ number of neutron
= nucleon number – protons number
= 36-17 = 19

8. Nuclide notation
NUCLEON
NUMBER
PROTON
NUMBER
A
Z
X
SYMBOL OF
ELEMENT
A nuclide is a type of nucleus with a particular proton number and a
particular nucleon number like isotopes for instance.

9. Isotopes


Atoms that have the same protons number but
diffferent nucleon number.
Isotopes of the same element has the same
chemical properties but different physical
characteristics

10. Examples of isotopes
 Carbon
13C
6
14C
6
12C
6
Carbon-13
Carbon-14
Carbon-12
 Uranium
232U
92
Uranium-232
234U
92
235U
92
Uranium-234
Uranium-235