An element 'X' belongs to 3rd period and group 17 of the periodic table. State its (i) electronic configuration, (ii) valency. Justify your answer with reasoning.

(i) Electronic Configuration of Element 'X':

• Configuration: $2, 8, 7$
• Reasoning: Since element 'X' belongs to the 3rd period, it has 3 electron shells ($K, L, M$). Since it belongs to group 17, it has 7 valence electrons in its outermost shell ($M$ shell). The inner shells ($K$ and $L$) must be completely filled with 2 and 8 electrons respectively. Thus, the electronic configuration is $2, 8, 7$.

(ii) Valency of Element 'X':

• Valency: $1$
• Reasoning: Valency is the combining capacity of an atom. For elements with 5 or more valence electrons, valency is calculated as $8 - \text{number of valence electrons}$. Since 'X' has 7 valence electrons, it needs to gain 1 electron to complete its stable octet configuration. Therefore, its valency is $8 - 7 = 1$.