Elements of Group 17 show the following properties except for *
a)The reducing nature of HX increases down the group
b)Thermal stability of HX decreases down the group
c)Volatility of halogen increases down the group
d)Boiling point of halogen increases down the group
Answers
Explanation:
) I
2
<F
2
<Br
2
<Cl
2
The electron affinity of Chlorine is maximum in the periodic table and so the bond dissociation enthalpy. Flourine has lower bond dissociation enthalpy than Br
2
and Cl
2
. Due to small size electronic repulsion is very high. I
2
has lowest bond dissociation enthalpy due to quite larger size it is easiest to break the bond.
(ii) HF<HCl<HBr<HI⇒Acidic strength of Halogen acids increases down the group.
(iii) BiH
3
<SbH
3
<AsH
3
<PH
3
<NH
3
⇒ Basic strength decreases down the group because as we go down the group the size of the atom and thus the electron density decreases. These compounds are lewis base having 1 lone pair on the central atoms. As the electron density decrease the tendency to donate electron pair decreases.
Option C is the incorrect property of the given statements.
- The reducing property of hydrogen halides generally increases down the group because the size of an atom increases as we go down the group. Hence the given property is true.
- The thermal stability of HX decreases down the group from top to bottom because the bond strength decreases as we go down the group and it is easier to break the bond. Hence the given property is true.
- Volatility implies the compound which easily evaporates in the atmosphere, the intermolecular forces increases as the molecular weight of the element is increasing. Hence elements with lower atomic weights are easily volatile.
- Hence the volatility order is F > Cl > Br > I. Hence the mentioned property is incorrect.
- The Boiling point of a halogen generally increases as we go down the group. Hence the mentioned property is correct.
Therefore, of the mentioned properties, Option C is the incorrect property.