NCERT Solutions for Class 12 Chemistry Chapter 7 the p-Block Elements in English and Hindi Medium updated for new academic session 2022-2023. Students of class 12 Chemistry get the intext and exercises question answers in video format also.

NCERT Solutions for Class 12 Chemistry Chapter 7

The p –Block Elements

The p-block elements are placed in groups 13 to 18 of the periodic table. Their valence shell electronic configuration is ns²np¹⁻⁶ (except He which has 1s² configuration).

Group 15 Elements
Group 15 includes nitrogen, phosphorus, arsenic, antimony, bismuth and moscovium. As we go down the group, there is a shift from nonmetallic to metallic through metalloidic character. Nitrogen and phosphorus are non-metals, arsenic and antimony metalloids, bismuth and moscovium are typical metals.

Class 12 Chemistry Chapter 7 MCQ

Q1

Which of the following statements is not correct for nitrogen?

[A]. Its electronegativity is very high
[B]. d-orbitals are available for bonding
[C]. It is a typical non-metal
[D]. Its molecular size is small
Q2

Boron shows diagonal relation with

[A]. Al
[B]. C
[C]. Si
[D]. Sn
Q3

Chlorine act as a bleaching agent in the presence of

[A]. Sunlight
[B]. Dry air
[C]. Moistures
[D]. Oxygen
Q4

On boiling phosphorus with KOH solution, product formed is

[A]. Potassium sulphate
[B]. Phosphorus pentoxide
[C]. Phosphorus hydroxide
[D]. Phosphine.

Electronic Configuration

The valence shell electronic configuration of these elements is ns²np³. The s orbital in these elements is completely filled and p orbitals are half-filled, making their electronic configuration extra stable.

Physical Properties
All the elements of this group are polyatomic. Dinitrogen is a diatomic gas while all others are solids. Metallic character increases down the group. Nitrogen and phosphorus are non-metals, arsenic and antimony metalloids and bismuth is a metal. This is due to decrease in ionisation enthalpy and increase in atomic size. The boiling points, in general, increase from top to bottom in the group but the melting point increases up to arsenic and then decreases up to bismuth. Except nitrogen, all the elements show allotropy.

Chemical Properties

The common oxidation states of these elements are –3, +3 and +5. The tendency to exhibit –3 oxidation state decreases down the group due to increase in size and metallic character. In fact last member of the group, bismuth hardly forms any compound in –3 oxidation state.

Dinitrogen
Dinitrogen is produced commercially by the liquefaction and fractional distillation of air. Liquid dinitrogen (b.p. 77.2 K) distils out first leaving behind liquid oxygen (b.p. 90 K). In the laboratory, dinitrogen is prepared by treating an aqueous solution of ammonium chloride with sodium nitrite.
NH₄CI (aq) + NaNO₂ (aq) ® N₂ (g) + 2H₂O(l) + NaCl (aq)

12th Chemistry Unit 7 Multiple Choice Questions

Q5

Main source of helium is

[A]. Air
[B]. Radium
[C]. Monazite
[D]. Water
Q6

Which one of the following elements is most metallic?

[A]. P
[B]. As
[C]. Sb
[D]. Bi
Q7

Which among the following factors is most important in making fluorine the strongest oxidising agent?

[A]. Electron affinity
[B]. Ionisation energy
[C]. Hydration energy
[D]. Bond dissociation energy.
Q8

Which one of the following elements is found in free state in nature?

[A]. Sodium
[B]. Iron
[C]. Zinc
[D]. Gold

Properties
Dinitrogen is a colourless, odourless, tasteless and non-toxic gas. Nitrogen atom has two stable isotopes: 14N and 15N. It has a very low solubility in water (23.2 cm3 per litre of water at 273 K and 1 bar pressure) and low freezing and boiling points.

Group 16 Elements

Oxygen, sulphur, selenium, tellurium, polonium and livermorium constitute Group 16 of the periodic table. This is sometimes known as group of chalcogens. Oxygen is the most abundant of all the elements on earth. Oxygen forms about 46.6% by mass of earth’s crust. Dry air contains 20.946% oxygen by volume. However, the abundance of sulphur in the earth’s crust is only 0.03-0.1%. Selenium and tellurium are also found as metal selenides and tellurides in sulphide ores. Polonium occurs in nature as a decay product of thorium and uranium minerals. Livermorium is a synthetic radioactive element.

Dioxygen and Ozone

Dioxygen
Dioxygen can be obtained in the laboratory by the following ways:
(i) By heating oxygen containing salts such as chlorates, nitrates and permanganates.
Ozone
Ozone is an allotropic form of oxygen. It is too reactive to remain for long in the atmosphere at sea level. At a height of about 20 kilometres, it is formed from atmospheric oxygen in the presence of sunlight. This ozone layer protects the earth’s surface from an excessive concentration of ultraviolet (UV) radiations.

Group 17 Elements

Fluorine, chlorine, bromine, iodine, astatine and tennessine are members of Group 17. These are collectively known as the halogens (Greek halo means salt and genes means born i.e., salt producers). The halogens are highly reactive non-metallic elements.

Group 18 Elements
Group 18 consists of elements: helium, neon, argon, krypton, xenon, radon and oganesson. All these are gases and chemically unreactive. They form very few compounds, because of this they are termed as noble gases. All these gases except radon and oganesson occur in the atmosphere. Their atmospheric abundance in dry air is ~ 1% by volume of which argon is the major constituent.

Class 12 Chemistry Chapter 7 Important Questions

What are p-block elements?

p-block elements are those in which the last electron occupies p-orbitals and are found in groups 13, 14, 15, 16, and 17 (except helium). Because p-block orbitals can only hold a maximum of six electrons, p-block elements are classified into six groups.

How many groups are there in p-block?

Consequently, there are six groups of p–block elements in the periodic table numbering from 13 to 18. Boron, carbon, nitrogen, oxygen, fluorine and helium head the groups.

Does p-block contain metals?

The p-block contains metal, nonmetal, and metalloid elements. Some of these elements are extremely abundant (oxygen, silicon), some are toxic (lead, arsenic), and some are very useful (tin, aluminum).

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