Other examples of ionic bonding
3 marks · NormalAn atom of potassium (K, atomic number 19) forms an ion.
Calculate:
The number of electrons in a potassium atom before ion formation.
The number of electrons in the potassium ion after it has formed.
The electronic configuration of the potassium ion.
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Show answer
(a) 19
(b) 18
(c) [2, 8, 8]
Show mark scheme and worked solution
Marking points
A1 (a) · 1 mark · Correct number of electrons in K atom: 19
A2 (b) · 1 mark · Correct number of electrons in K+ ion: 18
A3 (c) · 1 mark · States electronic configuration as [2, 8, 8]
Worked solution
a: Potassium atom (atomic number 19) has 19 electrons.
b: When it forms K+ ion, it loses 1 electron, so electrons = 19 – 1 = 18.
c: The electronic configuration is [2, 8, 8].