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

## Chapter 4: Atoms, Molecules and Radicals

#### Chapter 4: Atoms, Molecules and Radicals solutions [Page 0]

Define :-

Atom

Define :-

Molecule

Define:-

Define:-

Valency

Define:-

Periodic table

Write the names of the elements present in the :-

Common salt

Write the names of the elements present in the:-

Ammonia

Write the names of the elements present in the :-

Sulphuric acid

Write the names of the elements present in the :-

Glucose

Write the names of the elements present in the :-

Sodium hydroxide

Write the names of the elements present in the :-

Acetic acid

What does 2C02 represent ?

What does 2H2S  represent ?

What does 5H2S04 represent ?

What does 6NaNO3 represent ?

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

SO42

HC03

OH

Cr2072

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

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

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

Write the names of (NM_4)_2so_4 compounds :

Write the names of Ca(NO_3)_2 compounds :

Write the names of FeS compounds :

Write the names ofCuCo_3 compounds :

Write the names of Na_3PO_4 compounds :

Write the names of NH_4OH compounds :

Write the names of HgO compounds :

Write the names of ZnCl_2  compounds :

Write the names of ZnS compounds :

Write the names of H_2S  compounds :

Write the molecular formulae of Sodiun sulphide:

Write the molecular formulae of Aluminium sulphate :

Write the molecular formulae of Magenesium oxide :

Write the molecular formulae of Calcium hydroxide :

Write the molecular formulae of Hydrogen chloride :

Write the molecular formulae of Sulphuric acide :

Write the molecular formulae of Iron (II) sulphide :

Write the molecular formulae of Iron (III) sulphide :

Write the molecular formulae of Nitric acide :

Write the molecular formulae of Calcium phosphate :

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

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

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

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

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

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

Give the group number of following elements present in periodic table

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

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.

#### Chapter 4: Atoms, Molecules and Radicals solutions [Page 0]

Fill in the blank:

Atoms are .................

Fill in the blank

An ion with positive charge is called...............

Fill in the blank

An ion with negative charge is called ...............

Fill in the blank

2H2 means two ................ of hydrogen.

Fill in the blank

..................is a triatomic molecule.

Fill in the blank

Metals have ................ valency.

Fill in the blank

Chemical name of caustic soda is .................................

The valency of iron in Fe203 is

1. 1
2. 2
3. 3
4. 6

Which of the following has valency 4 ?

1. aluminium
2. oxygen
3. carbon
4. phosphorus

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

1. Ca(S04)2
2. Ca2(S04)
3. Ca(S04)3
4. CaS04

Which of the following exhibit variable valency ?

1. calcium
2. copper
3. carbon
4. chlorine

State the term.

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

State the term

The symbolic representation of a molecule ................

State the term

A group of atoms that react as a single unit ................

State the term

The combining capacity of an element......................

State the term

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

#### Chapter 4: Atoms, Molecules and Radicals solutions [Page 0]

Define

Ions

Define

Chemical bond

Define

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 ?

#### Chapter 4: Atoms, Molecules and Radicals solutions [Page 0]

Name the particles which revolve around the nucleus.

What are orbits or shells ?

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

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 Class 7 Chemistry chapter 4 - Atoms, Molecules and Radicals

Selina solutions for Class 7 Chemistry 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 Selina Concise Chemistry - Middle School for Class 7 (2018-19 Session) solutions in a manner that help students grasp basic concepts better and faster.

Further, we at Shaalaa.com are providing such solutions so that students can prepare for written exams. Selina textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 7 Chemistry 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.

Using Selina Class 7 solutions Atoms, Molecules and Radicals exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in Selina Solutions are important questions that can be asked in the final exam. Maximum students of CISCE Class 7 prefer Selina Textbook Solutions to score more in exam.

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