Page 21 - Chemistry_Form_2

Chemistry
for Secondary Schools

2 1 H , Mass number = 2

Number of proton = 1

Number of electron = 1
FOR ONLINE READING ONLY
Number of neutron = 2 – 1 = 1

3 1 H , Mass number = 3

Number of proton = 1
Number of electron = 1

Number of neutrons = 3 – 1 = 2

Example 1.4

An isotope of carbon has a mass number of 13 and an atomic number of 6.

(a) Write its nuclide notation.
(b) How many neutrons does it have?

(c) How many electrons does it have?

Solution

(a) 13 C
6
(b) Number of neutrons = 13 – 6 = 7

(c) Number of electrons = atomic number = 6

Many elements that occur naturally usually display isotopy. The most abundant

isotope of an element is taken to be the representative of that element. This
abundance is usually given in percentage. Examples of common elements that
display isotopy are hydrogen, oxygen, carbon, chlorine, nitrogen, and neon
(Table 1.3).

14 Student’s Book Form Two

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CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 14
CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 14 01/08/2025 11:20:51