Explain the trend of reducing property among alkaline earth metals.

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : The energy required to form ${\mathrm{Mg}}^{2+}$from $\mathrm{Mg}$ is much higher than that required to produce ${\mathrm{Mg}}^{+}$

Reason R:${\mathrm{Mg}}^{2+}$ is small ion and carry more charge than ${\mathrm{Mg}}^{+}$

In the light of the above statements, choose the correct answer from the options given below.

Given below are two statements: One is labelled as
Assertion $\mathbf{A}$ and the other is labelled as Reason $\mathbf{R}$
Assertion $\mathbf{A}$: Sodium is about $30$ times as abundant as potassium in the oceans.
Reason $\mathbf{R}$: Potassium is bigger in size than sodium.
In the light of the above statements, choose the correct answer from the options given below

${\mathrm{Be}}^{2+}$ is isoelectronic with which of the following ions