Question

Which of the following orders is wrong?
A. $N{H_3} < P{H_3} < As{H_3}$ - Acidic
B. $Li < B < Be < C$ - First IP
C. $A{l_2}{O_3} < MgO < N{a_2}O < {K_2}O$ - Basic
D. $L{i^ + } < N{a^ + } < {K^ + } < C{s^ + }$- Ionic radius

Answer 1

The substance which when added to water produces hydrogen ions ${H^ + }$ is called acid. $pH$ number less than $7$ is considered an acid.
Ionization potential is the amount of energy which is required to remove a loosely bound electron from the valence shell.
The basicity of a molecule is its ability to accept a proton so that it can form a stable product.
If we talk about Ionic radius, It is the distance from the nucleus of an ion up to which it has an influence on the electron cloud. When an atom loses or gains electrons the ions are formed.

Complete step by step answer:
In $group - 15$ , the hydrides have a lone pair on the central atom. On going down the group the size of the atom increases, which results in increasing the metallic character. Hence electron density over the $group - 15$ element decreases, hence electron donate tendency decreases. So, acidity increases down the group.
As the nuclear charge increases, the nuclear attraction on the valence electron increases .Hence the valence electrons are more tightly held. Therefore first ionization potential across the period increases.
Ionic radii increases down a group. In a group, all the ions have the same charge as they have the same valency (that is, the same number of valence electrons on the highest energy level sub-orbital). Therefore, ionic radii increase down a group as more shells are added.
Hence, option C is correct.

Note:
Do remember some exception of atoms in periodic table:
-As going from right to left on the periodic table, the atomic radius increases, and the ionization energy increases from left to right in the periods and up the groups. Exceptions to this trend is observed for alkaline earth metals ( $group - 2$ ) and nitrogen group elements ( $group - 15$ )
-The atomic radius of atoms generally decreases from left to right across a period. There are some small exceptions, such as the oxygen radius being slightly greater than the nitrogen radius. Within a period, protons are added to the nucleus as electrons are be in The electron affinities of the elements in $group - 15$ are larger (more negative) than the elements in $group - 1$ Elements in $group - 14$ have larger (more negative) electron affinities than elements in $group - 15$ added to the same principal energy level.