question_answer

The elements \[_{\mathbf{4}}\mathbf{Be}{{\mathbf{,}}_{\mathbf{12}}}\mathbf{Mg}\] and \[_{\mathbf{20}}\mathbf{Ca,}\] each having two valence electrons in their valence shells, are in periods 2, 3 and 4 respectively of the modern periodic table. Answer the following questions associated with these elements, giving reason in each case:

(a) In which group should they be?

(b) Which one of them is least reactive?

(c) Which one of them has the largest atomic size?

Answer:

\[_{4}Be=2,\text{ }2\]

\[_{12}Mg=2,\text{ }8\]

\[_{20}Ca=2,\text{ }8,\text{ }8,\text{ }2\]

(a) Group 2, they have 2 valence electrons

(b) Be, reactivity increases in a group.

(c) Ca, atomic size increases in a group.