Q.1 Explain the reactivity of elements of group 13, 14, 15 towards air/ oxygen with an
example each.
Answers
CHEMICAL PROPERTIES OF NITROGEN FAMILY - DEFINITION
Reducing nature: NH
3
<PH
3
<AsH
3
<SbH
3
<BiH
3
Basic nature: Ammonia is basic and form salts with acids. PH
3
is weakly basic. Rest others are not at all basic.
METHODS OF PREPARATION OF OXIDES OF NITROGEN FAMILY - DEFINITION
concept
Nitrogen has a strong tendency to form pπ-pπ multiple bonds between N and O atoms, whereas other elements of this group do not. Nitrogen forms five oxides with oxidation state from 1 to 5 while others show 3 and 5 only.
ACIDIC STRENGTH OF TRIOXIDES OF NITROGEN FAMILY - DEFINITION
N
2
O
3
>P
4
O
6
>As
4
O
6
>Sb
4
O
6
TREND IN OXIDISING AND REDUCING PROPERTIES OF CARBON FAMILY - DEFINITION
1. Sn in +2 oxidation state is reducing agent.
2. Lead compounds are stable in +2 state. Lead in +4 oxidation state acts as oxidizing agent, so the oxidizing and reducing nature from top to bottom become specific.
3. Carbon always present in +2 to +4 oxidation states.
DIFFERENT METHODS OF PREPARING HALIDES OF NITROGEN - DEFINITION
All the elements of group 15 form tri-halides of the type EX
3
and EX
5
. Nitrogen does not form pentahalide due to non-availability of the d-orbitals in its valence shell.
E= N, P, As, Sb and Bi.
X=F, Cl, Br and I.
OXIDATION STATES AND TRENDS IN CHEMICAL REACTIVITY OF BORON - DEFINITION
B and Al shows +3 oxidation state, but Ga, In, and Th due to inert pair effect, show oxidation states of both +1 and +3. According to Fajan rules, the small size of the ions and their charge of +3, favor the formation of covalent compounds.
TRIHALIDES OF NITROGEN FAMILY - DEFINITION
Trihalides have pyramidal structure. Three of the four sp
3
orbitals contains the lone pair of electrons. The bond angles of trihalides decrease as the electronegativity of the halogens increases. The order is PF
3
<PCl
3
<PBr
3
<PI
3
.
Trihalides of nitrogen are least stable. The trihalides readily undergo hydrolysis but the products of hydrolysis depends on the nature of the element. The trihalides of P, As and Sb due to the presence of d-orbitals accept a pair of electron.
REACTIVITY OF BORON TOWARDS AIR OR DIOXYGEN - DEFINITION
All the metals of group 13 react with dioxygen, however the reactivity increases down the group. They form trioxides at high temperature.
REACTIVITY TOWARDS ACIDS AND BASES - DEFINITION
Boron does not react with non-oxidising acids such as hydrochloric acid, all other elements reacts with oxidising and non-oxidising acids.
REACTIVITY OF BORON FAMILY TOWARDS HALOGENS - DEFINITION
Boron family react with halogens at high temperatures forming trihalides.
REACTIVITY OF CARBON TOWARDS OXYGEN AND THEIR PROPERTIES - DEFINITION
All the element of group 14 when heated in oxygen form oxides. These are mainly of two types, i.e., monoxides of the formula MO and dioxides of the formula MO
2
. These oxides shows the properties like acid-base character, reducing-oxidizing nature etc.
REACTIVITY OF CARBON FAMILY TOWARDS WATER AND THEIR PROPERTIES - DEFINITION
Carbon, silicon and germanium do not decomposes water at all. Tin decomposes steam to form tin oxide and dihydrogen gas.
REACTIVITY OF CARBON FAMILY TOWARDS HALOGENS AND THEIR PROPERTIES - DEFINITION
Except C all member of carbon series forms halides of formula MX
4
, which are covalent in nature.
PROPERTIES OF CARBON FAMILY - EXAMPLE
Memberes of this group form tetrahalides of type MX
4
and all alements of this group form oxides of the type MO
2
.