Other examples of ionic bonding
2 marks · EasyExplain, using electronic configuration, why a potassium ion (K+) has the same number of electrons as an argon atom.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
A potassium atom has 19 electrons. It loses one electron to form K+, so has 18 electrons, which is the same number as an argon atom.
Also accept: Both have 18 electrons; K+ is isoelectronic with Ar
Common mistakes: States K+ has 19 electrons
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Describes K atom has 19 electrons, loses one to form K+
A1 · 1 mark · States K+ and Ar both have 18 electrons
Worked solution
A potassium atom has 19 electrons. When it forms a K+ ion, it loses one electron and so has 18 electrons. This is the same as an argon atom, which has 18 electrons.