Other examples of ionic bonding

2 marks · Easy

A fluorine atom (atomic number 9) forms a fluoride ion. Calculate: (i) The number of protons in the fluoride ion. (ii) The number of electrons in the fluoride ion. Give both answers.

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(i) 9 protons

(ii) 10 electrons

Common mistakes: Protons = 10; Electrons = 9

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Marking points

B1 · 1 mark · States 9 protons

B1 · 1 mark · States 10 electrons

Worked solution

Protons (atomic number) = 9. Fluoride ion (F–) has gained one extra electron compared to the atom, so electrons = 9 + 1 = 10.