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# Selina solutions for Concise Chemistry Class 7 ICSE chapter 4 - Atoms, Molecules and Radicals [Latest edition]

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## Chapter 4: Atoms, Molecules and Radicals

#### Selina solutions for Concise Chemistry Class 7 ICSE Chapter 4 Atoms, Molecules and Radicals Exercise

Exercise | Q 1.1

Define:- Atom

Exercise | Q 1.2

Define:- Molecule

Exercise | Q 1.3

Exercise | Q 1.4

Define:- Valency

Exercise | Q 1.5

Define:- Periodic table

Exercise | Q 2.1

Write the names of the elements present in the:-

Common salt

Exercise | Q 2.2

Write the names of the elements present in the:-

Ammonia

Exercise | Q 2.3

Write the names of the elements present in the :-

Sulphuric acid

Exercise | Q 2.4

Write the names of the elements present in the:-

Glucose

Exercise | Q 2.5

Write the names of the elements present in the:-

Sodium hydroxide

Exercise | Q 2.6

Write the names of the elements present in the:-

Acetic acid

Exercise | Q 3.1

What does 2C02 represent ?

Exercise | Q 3.2

What does 2H2S  represent ?

Exercise | Q 3.3

What does 5H2S04 represent ?

Exercise | Q 3.4

What does 6NaNO3 represent ?

Exercise | Q 4

Write the symbols and valencies of the following radicals:

(a)Magnesium iron

(b) Amonium

(c)carbonate

(d)Nitrate

(e)Oxied

(f) Bisulphate

(g) Aluminium ion

Exercise | Q 5.1

SO42

Exercise | Q 5.2

HC03

Exercise | Q 5.3

OH

Exercise | Q 5.4

Cr2072

Exercise | Q 6.1

Name one ion for  each of the valencies +1, +2  and +3.

Exercise | Q 6.2

Name one ion for  each of the valencies-1, -2  and -3.

Exercise | Q 7

The valency of calcium is 2. Write the valencies of other radical in the following :

1. CaO
2. Ca(OH)2
3. CaC03
4. CaCl2
Exercise | Q 8.1

Write the names of ("NM"_4)_2"SO"_4 compounds :

Exercise | Q 8.2

Write the names of "Ca"("NO"_3)_2 compounds :

Exercise | Q 8.3

Write the names of "FeS" compounds :

Exercise | Q 8.4

Write the names of "Na"_3"PO"_4 compounds :

Exercise | Q 8.4

Write the names of "CuCo"_3 compounds :

Exercise | Q 8.5

Write the names of "NH"_4"OH" compounds :

Exercise | Q 8.6

Write the names of "HgO" compounds :

Exercise | Q 8.7

Write the names of "ZnCl"_2  compounds :

Exercise | Q 8.8

Write the names of ZnS compounds :

Exercise | Q 8.9

Write the names of "H"_2"S" compounds :

Exercise | Q 9.01

Write the molecular formulae of Sodiun sulphide:

Exercise | Q 9.02

Write the molecular formulae of Magenesium oxide :

Exercise | Q 9.03

Write the molecular formulae of Calcium hydroxide :

Exercise | Q 9.04

Write the molecular formulae of Hydrogen chloride :

Exercise | Q 9.05

Write the molecular formulae of Sulphuric acide :

Exercise | Q 9.06

Write the molecular formulae of Iron (II) sulphide :

Exercise | Q 9.07

Write the molecular formulae of Iron (III) sulphide:

Exercise | Q 9.08

Write the molecular formulae of Nitric acide :

Exercise | Q 9.09

Write the molecular formulae of Calcium phosphate :

Exercise | Q 9.1

Write the molecular formulae of Aluminium sulphate :

Exercise | Q 9.11

Write the molecular formulae of Magnesium nitride:

Exercise | Q 10.1

The valency of sodium is one, write the molecular formula for sodium oxide ?

Exercise | Q 10.2

The valency of sodium is one, write the molecular formula for sodium sulphate ?

Exercise | Q 10.3

The valency of sodium is one, write the molecular formula for sodium carbonate ?

Exercise | Q 10.4

The valency of sodium is one, write the molecular formula for sodium hydroxide ?

Exercise | Q 10.5

The valency of sodium is one, write the molecular formula for sodium nitratev ?

Exercise | Q 11

What is variable valency ? Give two examples of elements showing variable valency.

Exercise | Q 12

Give the group number of following elements present in periodic table

Exercise | Q 13

An element belongs to group VA. What would be its valency? Name two such elements.

Exercise | Q 14

An element belongs to group II. What would be its valency? Write the formula of molcules of compounds it will form with elements in VA, VIA and VIIA groups.

#### Selina solutions for Concise Chemistry Class 7 ICSE Chapter 4 Atoms, Molecules and Radicals Exercise Objective type questions

Objective type questions | Q 1.1

Fill in the blank:

Atoms are _____

Objective type questions | Q 1.2

Fill in the blank

An ion with positive charge is called ______

Objective type questions | Q 1.3

Fill in the blank

An ion with negative charge is called _______

Objective type questions | Q 1.4

Fill in the blank

2H2 means two _______ of hydrogen.

Objective type questions | Q 1.5

Fill in the blank

_______ is a triatomic molecule.

Objective type questions | Q 1.6

Fill in the blank

Metals have ______ valency.

Objective type questions | Q 1.7

Fill in the blank

Chemical name of caustic soda is _______

Objective type questions | Q 2.1

The valency of iron in Fe203 is

• 1

• 2

• 3

• 6

Objective type questions | Q 2.2

Which of the following has valency 4 ?

• aluminium

• oxygen

• carbon

• phosphorus

Objective type questions | Q 2.3

The sulphate radical is written as S042-. What is the formula of calcium sulphate ?

• Ca(S04)2

• Ca2(S04

• Ca(S04)

• CaS0

Objective type questions | Q 2.4

Which of the following exhibit variable valency ?

• calcium

• copper

• carbon

• chlorine

Objective type questions | Q 3.1

State the term.

The number of atoms present in a molecule of an element _________

Objective type questions | Q 3.2

State the term

The symbolic representation of a molecule ______

Objective type questions | Q 3.3

State the term

A group of atoms that react as a single unit ______

Objective type questions | Q 3.4

State the term

The combining capacity of an element _______

Objective type questions | Q 3.5

State the term

The tabular arrangement of elements in horizontal rows and vertical columns _________

#### Selina solutions for Concise Chemistry Class 7 ICSE Chapter 4 Atoms, Molecules and Radicals Exercise Additional questions

Define: Ions

Define: Chemical bond

Define: Atomic number

Define: Mass number

Define: Relative atomic mass

What does an atom consist of ? Explain.

Give the charge and the mass of an electron, proton and neutron present in an atom ?

Name two particles found inside the nucleus. What are they collectively called ?

Name the particles which revolve around the nucleus.

What are orbits or shells ?

What is the maximum number of electrons present in:

1. first shell
2. second shell
3. third shell and
4. fourth shell

Elements X and Y have 1 and 7 electrons in their outermost shell respectively.

Which element will lose electron?

Elements X and Y have 1 and 7 electrons in their outermost shell respectively.

Which element will gain electron?

Elements X and Y have 1 and 7 electrons in their outermost shell respectively.

Which will form positive ion?

Elements X and Y have 1 and 7 electrons in their outermost shell respectively.

Which will form negative ion?

Elements X and Y have 1 and 7 electrons in their outermost shell respectively.

What will be the charge present of the molecule XY after chemical combination?

What is the number of electrons donated by a magnesium atom and number of electrons accepted by a sulphur atom during their chemical combination?

How many units of charge are developed on each atom?

What is the number of electrons after the transfer of electrons in magnesium and sulphur atoms.

Diagrammatically represent the transfer of electrons.

What do you understand by the following terms valency, valence electrons and valence shell?

Name the following radicals and give their valencies:

1. SO4
2. CO3
3. OH4.
4.Cr2O7

What is variable valency ? Give two examples of elements showing variable valency.

Name three elements each whose ions have valency +1, +2 and +3 respectively

Name three non-metals/radicals which have valency -1, -2, and -3.

Define: Ionic bond

Define: Covalent bond

Give two examples for each of ionic and covalent bond.

Write electronic configuration of oxygen, fluorine, sodium, silicon, argon.

Who originated the word ‘atom’ ?

What does the word ‘atom’ mean?

State Dalton’s atomic theory.

How did Neils Bohr visualise the atom ?

Name the particle or particles you would expect to find in :

The orbit of an atom

Name the particle or particles you would expect to find in :

The nucleus of an atom

An atom has 13 protons and 14 neutrons.

What is the atomic number of the atom ?

An atom has 13 protons and 14 neutrons.

How many electrons would be present in this atom ?

An atom has 13 protons and 14 neutrons.

What is the atomic mass of the atom ?

Define: An Atom:

Define: Atomic number

Define: Mass number :

Define: Atomic weight :

A certain particle ‘X’ has 17 protons, 18 electrons and 20 neutrons.

What is such a particle called ?

A certain particle ‘X’ has 17 protons, 18 electrons and 20 neutrons.

What is the mass number of X ?

A certain particle ‘X’ has 17 protons, 18 electrons and 20 neutrons.

What is the atomic numebr of X ?

A certain particle ‘X’ has 17 protons, 18 electrons and 20 neutrons.

Does the particle have an excess of electrons or a deficiency of electrons ?

A certain particle ‘X’ has 17 protons, 18 electrons and 20 neutrons.

What is the charge on the particle ?

Fill in the blank

If an atom gains an electron, it is called an _______

Fill in the blank

If an atom loses an electron, it acquires ______ a charge.

Fill in the blank

A charged particle is called an _____

Fill in the blank

An _______ is electrically neutral.

Fill in the blank

An excess of electrons produces a ________ charge.

Fill in the blank

A deficiency of electrons produces a ________ charge.

## Selina solutions for Concise Chemistry Class 7 ICSE chapter 4 - Atoms, Molecules and Radicals

Selina solutions for Concise Chemistry Class 7 ICSE chapter 4 (Atoms, Molecules and Radicals) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CISCE Concise Chemistry Class 7 ICSE solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Concise Chemistry Class 7 ICSE chapter 4 Atoms, Molecules and Radicals are Concept of Atoms, Molecules and Radicals, Concept of Independent Existence, Properties of an Element Depend Upon the Atoms Constituting It, Concept of Molecule, Concept of Radical, Atomicity of Elements and Compounds – Mono Atomic, Diatomic, Triatomic, Polyatomic, Elements in the Periodic Table with Their Names and Symbols, Concept of Valency, Concept of Atomic Structure.

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