Class 11 NEET Chemistry Classification Of Elements And Periodicity In Properties

Concept:Metallic character decreases across a period from left to right and increases down a group.So the least metallic element has the highest electronegativity, and the most metallic element has the lowest electronegativity.Explanation:Among the given period 3 elements, the order of metallic character is:$\mathrm{Na} > \mathrm{Mg} > \mathrm{Si} > \mathrm{P}$.Thus $\mathrm{P}$ is the least metallic and $\mathrm{Na}$ is the most metallic among these period 3 elements.$\mathrm{Be}$ lies above $\mathrm{Mg}$ in group 2, so metallic character increases down the group:$\mathrm{Mg} > \mathrm{Be}$.Also, $\mathrm{Be}$ is a metal while $\mathrm{Si}$ is a metalloid, and their electronegativity values support this order.Using approximate Pauling electronegativities: $\mathrm{Na}=0.9$, $\mathrm{Mg}=1.2$, $\mathrm{Be}=1.5$, $\mathrm{Si}=1.8$, $\mathrm{P}=2.1$.Higher electronegativity means lower metallic character.Therefore, increasing metallic character means decreasing electronegativity:$\mathrm{P} < \mathrm{Si} < \mathrm{Be} < \mathrm{Mg} < \mathrm{Na}$.Answer:Option A: $\mathrm{P} < \mathrm{Si} < \mathrm{Be} < \mathrm{Mg} < \mathrm{Na}$