BECE Science 2023 Paper

Question : 27

Total: 40

Which of the following ions is formed by the loss of 2 electrons?

$\mathrm{Ca}^{2+}$
$\mathrm{S}^{2-}$
$\mathrm{K}^{+}$
$\mathrm{F}^{-}$

Solution:

Concept:

An atom that loses electrons becomes a positive ion (cation); its charge equals the number of electrons lost. An atom that gains electrons becomes a negative ion (anion).

Explanation:

\mathrm{Ca}^{2+}

: calcium (2,8,8,2) loses its 2 outer electrons, so it is formed by the loss of 2 electrons.

\mathrm{K}^{+}

: loss of 1 electron.

\mathrm{S}^{2-}

and

\mathrm{F}^{-}

: formed by gaining electrons.

Answer:

Option A (

\mathrm{Ca}^{2+}

)

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