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# Selina solutions for Class 8 Chemistry chapter 4 - Atomic Structure

## Chapter 4: Atomic Structure

#### Chapter 4: Atomic Structure solutions [Page 0]

Fill in the blank

Dalton ................... that atoms could not be divided .

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An ion which has a positive charge is called a ..................

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The outermost shell of an atom is known as............................

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The ..........................of an atom is very hard and dense.

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Neutrons are .......................... particles having mass equal to that of protons.

Fill in the blank

Isotopes are the atoms of.......... element having the same atomic number but a different mass number

Write true or false for the following statement

An atom on the whole has a positive charge.

Write true or false for the following statement

The maximum number of electrons in the first shell can be 8.

Write true or false for the following statement

The central pad of the atom is called nucleus.

Give the following a suitable word/phrase

The sub-atomic particle with negative charge and negligible mass.

Give the following a suitable word/phrase.

Protons and neutrons present in the nucleus.

Give the following a suitable word/phrase.

The electrons present in the outermost shell.

Give the following a suitable word/phrase

Arrangement of electrons in the shells of an atom.

Give the following a suitable word/phrase.

The number of protons present in the nucleus of an atom.

Give the following a suitable word/phrase.

The sum of the number of protons and neutrons of an atom.

Give the following a suitable word/phrase.

Atoms of same element with same atomic number but a different mass number.

Give the following a suitable word/phrase.

The smallest unit of an element which takes part in a chemical reaction.

Multiple Choice Questions

The outermost shell of an atom is known as

1. valency
2. valence electrons
3. nucleus
4. valence shell

Multiple Choice Questions

number of valence electrons present in magnesium is

1. two
2. three
3. four
4. five

Multiple Choice Questions

The sub atomic particle with negative charge is

1. proton
2. neutron
3. electron
4. nucleon

Multiple Choice Questions

] If the atomic number of an atom is 17 and mass number is 35 then number of neutron will be

1. 35
2. 17
3. 18
4. 52

Multiple Choice Questions

The number of electrons in an atom is equal to number of

1. protons in a neutral atom
2. neutrons in a neutral atom
3. nucleons in a neutral atom
4. none of the above

Multiple Choice Questions

The sum of number of protons and number of neutrons present in the nucleus of an atom is called its

1. mass number
2. atomic number
3. number of electrons
4. all of the above

Name three fundamental particles of the atom. Give the symbol with charge, on each particle.

Define the following terms:
(a) Atomic number
(b) Mass number
(c) Nucleons
(d) Valence shel

Mention briefly the salient features of Dalton’s atomic theory (five points)

(a) What are the two main features of Rutherford’s atomic model?
(b) State its one drawback

What are the observations of the experiment done by Rutherford in order to determine the structure of an atom?

State the mass number, the atomic number, number of neutrons and electronic configuration of the following atoms.
""^12""_6C  ,   ""^16""_8O     ,   ""^19""_9F  ,   ""^20""_10Ne     ,  ""_13""Al""^27   ,   ""_17""Cl""^35
Also, draw atomic diagrams for them.

What is variable valency? Name two elements having variable valency and state their valencies.

The atomic number and the mass number of sodium are 11 and 23 respectively. What information is conveyed by this statement.

Draw the diagrams representing the atomic structures of the following:
(a) Nitrogen (b) Neon

Explain the rule with example according to which electrons are filled in various energy levels

The atom of an element is made up of 4 protons, 5 neutrons and 4 electrons. What is its atomic number and mass number?

(a) What are the two main parts of which an atom is made of?
(b) Where is the nucleus of an atom situated ?
(c) What are orbits or shells of an atom ?

What are isotopes? How does the existence of isotopes contradict Dalton’s atomic theory?

Complete the table below by identifying A, B, C, D, E andF

#### Chapter 4: Atomic Structure solutions [Page 0]

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Atomic theory of matter was given by ..........................

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Gases become good conductors of electricity under ........ (low/high) pressure and .............. (low/high) voltage electrical discharge.

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Rutherford won the Nobel Prize in 1908 for his investigations in the field of ......................

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The electrons revolving in shells close to the nucleus are called ................... electrons.

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In an atom, the last shell containing electrons is called its..................shell.

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The protons and neutrons are held firmly in the nucleus by strong .........................

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Amount of energy stored inside the ..................... is known as nuclear energy.

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The γ-rays are............................ radiations, like light.

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Nuclear energy can be used to make ..........................

Which of these have similar chemical properties but different set of physical properties and mass number?

1. isobars
2. elements
3. isotopes
4. none of these

Which one of the following scientists put forward the theory regarding the extra-nuclear structure of the atom?

2. John Dalton
3. Rutherford
4. Niels Bohr

Which of the following scientists observed that cathode rays consists of negatively charged particles?

1. John Dalton
2. J J Thomson
4. Democritus

In 1908, R A Millikan found the charge of an electron to be

1. 1.6 x 10-19 C
2. 1.6 x 10-15 C
3. 1.4 x 10-19 C
4. 1.6 x 19-16 C.

Who discovered that radioactive rays are given out by uranium?

1. Henri Becquerel
2. Marie Curie
3. Pierre Curie
4. Schmidt

How many times is a proton heavier than an electron?

1. 1500
2. 1800
3. 1840
4. none of these

β-particles are actually a stream of

1. protons
2. electrons
3. neutrons
4. none of these

Which of the following is used as a coolant in nuclear reactor?

1. liquid sodium
2. liquid nitrogen
4. plutonium

MATCH THE COLUMNAS

 1. Jpham  Dalton a. Neutrons 2. Atom b. Model of the atom 3. Chadwick c.The atomic theory of matter 4. Rutherfrod d. Positively  charged 5. Protons e. Electricity neutral 6. Nuclear  fusion f. Generator of electricity 7.Gamma -rays g. High penetrating power h.Energy in sun

TRUE \ FALSE

Elements combine in definite proportions to form compounds.

TRUE \ FALSE

Elements having a tendency to accept electrons are called metals

TRUE \ FALSE

Electrons are present in the nucleus.

TRUE \ FALSE

Neils Bohr gave the theory to explain the arrangement of protons in an atom.

TRUE \ FALSE

Cathode rays are a stream of fast moving particles that travel in random directions.

TRUE \ FALSE

Uranium-235 and uranium-238 both undergo nuclear fission.

TRUE \ FALSE

After the emission of a beta-particle, the atomic number of the atom increases by one.

#### Chapter 4: Atomic Structure solutions [Page 0]

What is an atom?

Describe a discharge tube.

What is the central part of an atom known as?

What do you mean by electron transition?

Define an ionic compound.

Define the atomic mass number of an atom.

Name the isotopes of hydrogen.

Name three inert gases.

What is the charge on a neutron ?

What is the number of neutrons present in a potassium atom ?

#### Chapter 4: Atomic Structure solutions [Page 0]

State the postulates of the Dalton’s atomic theory.

Name the three subatomic particles. How are they different from each other ?

Enlist the features of Bohr’s model of an atom. How did he correct the Rutherford’s model ?

What is the maximum number of electrons that L shell can accommodate ? Give reasons for your answer.

Draw the electronic configuration of the following elements clearly stating the number of neutrons and protons in their nucleus.
a. Beryllium b. Silicon
c. Chlorine d. Aluminium
e. Nitrogen

How are isobars different from isotopes ?

Write a note on valence shell.

What are the various components of a nuclear power plant?

## Selina solutions for Class 8 Chemistry chapter 4 - Atomic Structure

Selina solutions for Class 8 Chemistry chapter 4 (Atomic Structure) 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 8 (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 8 Chemistry chapter 4 Atomic Structure are Fundamental Subatomic Particles Present in an Atom: Electrons, Protons, Neutrons, Nucleus and Extra Nuclear Parts, Concept of Atomic Number and Mass Number, Concept for Atomic Structure.

Using Selina Class 8 solutions Atomic Structure 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 8 prefer Selina Textbook Solutions to score more in exam.

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