Q10 of 58 Page 1

An element ‘M’ with electronic configuration (2, 8, 2) combines separately with (NO3)-, (SO4)2- and (PO4)3- radicals. Write the formula of the three compounds so formed. To which group and period of the Modern Periodic Table do the elements 'M' belong? Will 'M' form covalent or ionic compounds? Give reason to justify your answer.

The electronic configuration 2,8,2 shows that there are 2 valance electrons in the outermost shell hence it belongs to group two and it has 3 shells (K, L, M) thus belongs to period three.


The Group Number tells us the number of valance electrons


The Period Number tell us the number of shells


M is magnesium (2,8,2) with atomic number 12.


The chemical formula of the compounds formed are:


(i) Mg2+ + NO3-→ Mg (NO3)2 (magnesium nitrate)


(ii) Mg2+ + SO42-→ Mg (SO4)(magnesium sulphate)


(iii) Mg2+ + PO43-→ Mg3 (PO4)2 (magnesium phosphate)


‘M’ will form ionic compounds by losing two valence electrons to achieve a noble gas configuration, that is, a stable octet in the valence shell.


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