Question

Atoms of eight elements A, B, C, D, E, F, G and H have the same number of electronic shells but different number of electrons in their outermost shell. It was found that elements A and G combine to form an ionic compound which can also be extracted from sea water. This compound is added in a small amount to almost all vegetable dishes during cooking. Oxides of elements A and B are basic in nature while those of E and F are acidic. The oxide of D is almost neutral. Based on the above information answer the following question.

If the number of electrons in the outermost shell of elements and be 3 and 7 respectively, write the formula of the compound formed by the combination of C and G.

Answer 1

$\Rightarrow$ Number of given elements are $8$. They are $A,B,C,D,E,F,G$ and $H$.

$\Rightarrow$ All $8$ elements belong to the same period because they have the same number of electronic shells and have different number of electrons in the outermost shell.

$\Rightarrow$ We can see the above pattern in $3^{rd}$ period as it have $8$ elements.

$\Rightarrow$ Here $\Rightarrow$ $A=Na$ (Sodium), $B=Mg$ (Magnesium),

$C=Al$ (aluminium), $D=Si$ (Silicon),

$E=P$ (Phosphorus), $F=S$ (Sulphur),

$G=Cl$ (Chlorine), $H=Ar$ (Argon).

$C$ and $G$ reacts and forms a compound having a formula ${CG}_3$ : Where $C=$ Aluminium and $G=$ Chlorine.

$\Rightarrow {AlCl}_3$

It is because valency of Al is 3 and that of Cl is 1.