Page 19 - Chemistry_Form_2

Chemistry
for Secondary Schools

Example 1.2

Potassium (K) atom has 19 electrons and the mass number of 39.

(a) Work out the:
FOR ONLINE READING ONLY
(i) atomic number, and
(ii) number of neutrons.

(b) Give the nuclide notation.
(c) Show the representation of the nucleus of the potassium atom.

(d) Draw the electronic configuration of potassium.

Solution

(a) (i) Atomic number = number of protons = number of electrons = 19

(ii) Mass number = number of protons + number of neutrons
Number of neutrons = mass number – number of protons

= 39 – 19
= 20

(b) 39 K ; where 39 is the mass number and 19 the atomic number.
19

(c)

(d)

12 Student’s Book Form Two

01/08/2025 11:20:51
CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 12 01/08/2025 11:20:51
CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 12