Observe the following statements. Statement (A) In general, the ionisation potential value decreases on…
Observe the following statements.
Statement (A) In general, the ionisation potential value decreases on moving down in the group.
Statement (B) The lst ionisation potential of sodium is greater from that of potassium. Correct answer is
Both $A$ and $B$ are incorrect.
Both $A$ and $B$ are correct.
$A$ is correct but $B$ is incorrect.
$A$ is incorrect but $B$ is correct.
Solution
Ionisation energy is the energy required to remove an electron from an isolated gaseous atom. Ionisation potential decreases as we move down in the group. The atomic number increases in a group and hence the number of shells also increases. Thus, outermost electrons are far away from nucleus and can be removed easily.
Hence, statement A is correct
The outer electron in potassium is in $4 s$-orbital, which is further away from the nucleus than the $3 s$-orbital of sodium. This means that less energy is needed to remove the outermost electron. Therefore, first ionisation potential of sodium is greater than potassium.
Hence, statement (b) is also correct.