Question

Choose incorrect statements of the following:-
$(a)$ Density of sodium is more than potassium
$(b)$ Size of chlorine is more than sodium
$(c)$ $I.P.$ of sulphur is more than phosphorous
$(d)$ Electron affinity of sulphur is more than oxygen

• A. Only $b,c$
• B. Only $a,c,d$
• C. Only $c$
• D. Only $b,c,d$

Answer 1

Answer: (A)

1. In alkali metals, atomic weight increases down the group.
In the case of potassium and sodium, $d-$ orbitals present in potassium, which increases the volume of potassium. Thereby density of potassium decreases. So Potassium has a low density than Sodium.
Hence, statement $a$ is correct.
2. Due to an increase in the number of electrons in the case of chlorine, the total nuclear charge increases which tends to tightly hold up the valence electrons.
Due to more force of attraction the atomic size of chlorine decreases. Hence, the sodium atom is much larger than the chlorine atom.
Hence, statement $b$ is incorrect.
3. Ionisation enthalpy of phosphorus is greater than sulphur because the phosphorus has stable half filled electronic configuration i.e $3p^3$ but sulphur do not have stable configuration.
Hence, statement $c$ is incorrect.
4. Oxygen is smaller in size than sulfur, has its valence shell electrons placed more closely than sulfur. S0 the overall electron affinity of the oxygen comes out to be lesser than that of sulfur.
Hence, statement $d$ is correct.