Geometric Representation of Atomic Structure Class-8th Goyal Brothers ICSE Chemistry Solutions ch-4 unit-2

Geometric Representation of Atomic Structure Class-8th Goyal Brothers ICSE Chemistry Solutions Ch-4 (Atomic Structure) Unit-2(Geometric Representation of Atomic Structure). We Provide Step by Step Answers of Objectives, True and False, Incorrect and Correct , Definitions , Match the followings and Short/Long Question Type answers of Ch-4(Atomic Structure) Unit-2(Geometric Representation of Atomic Structure). Visit official Website  CISCE  for detail information about ICSE Board Class-8

Geometric Representation of Atomic Structure Class-8th Goyal Brothers ICSE Chemistry Solutions ch-4 unit-2

Board	ICSE
Class	8th
Subject	Chemistry
Book Name	Goyal Brothers
Chapter-4	Atomic Structure
Unit-2	Geometric Representation of Atomic Structure
Topic	Solution of exercise questions
Session	2023-24

OBJECTIVE TYPE QUESTIONS

Geometric Representation of Atomic Structure Class-8th Goyal Brothers ICSE Chemistry Solutions ch-4 unit-2

Que: A. Fill in the blank spaces by choosing the correct words from the given list :

List : 2, 8, 8, 2; twenty seven, eight, two, nuclear

1. The L-shell of an atom can have maximum of eight electrons.

2. Tritium, an isotope of hydrogen gas, two neutrons in its nucleus.

3. In an atom of _13Al²⁷, the number of nucleons are twenty seven.

4. The electronic configuration of _40Ca²⁰ is 2, 8, 8, 2.

5. The attractive forces between the nucleons nuclear.

Que: B. Statements given below are incorrect. Write the correct statements :

Question: 1. M-shell of an atom can have maximum of eight electrons.

Answer: M-shell of an atom can have maximum of 18 electrons.

Question: 2. The atoms of different elements having same mass number, but different atomic number are called isotopes.

Answer: The atoms of different elements having same mass number, but different atomic number are called isobars.

Question: 3. Deuterium an isotope of hydrogen has two neutrons in its nucleus.

Answer: Deuterium an isotope of hydrogen has three neutrons in its nucleus.

Question: 4. The electronic configuration of ₁₉K³⁹ is 2, 9, 8.

Answer: The electronic configuration of ₁₉K³⁹ is 2, 8, 8.

Question: 5. Helium, a noble gas has eight electrons in its valence shell.

Answer: Helium, a noble gas has eight electrons in its outermost shell.

Que: C. Match the statements in Column A, with those in Column B :

Column A	Column B
1. Atoms of same elements having same atomic number, but different mass numbers.	(a) Helium
2. An isotope of hydrogen.	(b) Isotopes
3. The maximum number of electrons in the valence shell of an atom.	(c) 2, 8, 5
4. The lightest noble gas.	(d) Deuterium
5. The electronic configuration of phosphorus 15P31.	(e) 8

Answer: 

Column A	Column B
1. Atoms of same elements having same atomic number, but different mass numbers.	(a) Isotopes
2. An isotope of hydrogen.	(b) Deuterium
3. The maximum number of electrons in the valence shell of an atom.	(c) 8
4. The lightest noble gas.	(d) Helium
5. The electronic configuration of phosphorus 15P31.	(e) 2, 8, 5

Que: D. Write ‘True’ or ‘False’ for the following statements :

Statements	True/False
1. Helium is the only gas which has 2 electrons in its valence shell.	T
2. 6C12 denotes that element carbon has mass number of 6 and atomic number 12.	F
3. K-shell of an atom can accommodate maximum of eight electrons.	F
4. The number of neutrons in an atom of 17Ca37 are 17.	T
5. Electronic configuration of all isotopes of an elements is different.	F

Que: E. Tick (√) the most appropriate answer :

1. The isotopes of a same element have :

(a) same mass number

(b) same atomic number

(c) different mass number

(d) (b) and (c) both

Answer: option (d) (b) and (c) both is correct.

2. The electronic configuration of sodium [1123Na] is :

(a) 2, 8, 8, 6

(b) 2, 8, 1

(c) 2, 9

(d) 2, 18, 4

Answer: option (b) 2, 8, 1 is correct.

3. With the exception of helium all noble gases have …………… electrons in their valence shell.

(a) 2

(b) 18

(c) 8

(d) 32

Answer: option (a) 2 is correct.

4. The maximum number of electrons in L-shell are

(a) 2

(b) 32

(c) 18

(d) 8

Answer: option (d) 8 is correct.

5. The atoms of same elements having different physical properties, but same chemical properties are called :

(a) allotropes

(b) isobars

(c) isotopes

(d) both (a) and (c)

Answer: option (c) isotopes is correct.

STUDY QUESTIONS

Geometric Representation of Atomic Structure Class-8th Goyal Brothers ICSE Chemistry Solutions ch-4 unit-2

Question: 1. Write the number of (a) protons, (b) neutrons, (c) electrons is case of following atoms :

(i) Neon [₁₀Ne²⁰]

Answer: (a) protons = 10

(b) neutrons = 20 – 10 = 10

(c) electrons = 10

(ii) Aluminum [₁₃Al²⁷]

Answer: (a) protons = 13

(b) neutrons = 27 – 13 = 14

(c) electrons = 13

(iii) Fluorine [₉F¹⁹]

Answer: (a) protons = 9

(b) neutrons = 19 – 9 = 10

(c) electrons = 9

(iv) Potassium [₁₉K³⁹]

Answer: (a) protons = 19

(b) neutrons = 39 – 19 = 20

(c) electrons = 19

Question: 2. Write the electronic distribution of the following atoms along with the name of electron shell.

(a) Sodium [₁₁Na²³]

Answer: The distribution of electrons in the sodium atom is as follows:

• In the first orbit or K-shell = 2 electrons
• In the second orbit or L-shell = 8 electrons
• In the third orbit or M-shell = 1 electron
• Or, we can write the distribution of electrons in a sodium atom as 2, 8, 1.

(b) Nitrogen [₇N¹⁴]

Answer: The distribution of electrons in the Nitrogen atom is as follows:

• In the first orbit or K-shell = 2 electrons
• In the second orbit or L-shell = 5 electrons
• Or, we can write the distribution of electrons in a sodium atom as 2, 5.

(c) Silicon [₁₄Si²⁹]

Answer: The distribution of electrons in the silicon atom is as follows:

• In the first orbit or K-shell = 2 electrons
• In the second orbit or L-shell = 8 electrons
• In the third orbit or M-shell = 4 electron
• Or, we can write the distribution of electrons in a sodium atom as 2, 8, 4.

(d) Sulphur [₁₆S³²]

Answer: The distribution of electrons in the Sulphur atom is as follows:

• In the first orbit or K-shell = 2 electrons
• In the second orbit or L-shell = 8 electrons
• In the third orbit or M-shell = 6 electron
• Or, we can write the distribution of electrons in a sodium atom as 2, 8, 6.

Question: 3. Define (a) atomic number (b) mass number.

Answer: (a) Atomic number: Atomic number refers to the number of protons present in an atom. It is denoted by Z. Example: An atom of oxygen contains 8 proton Therefore its atomic number is 8.
(b) Mass number: Mass number refers to the sum of the number of protons and neutrons present in
the nucleus of an atom and denoted by A Mass number = Number of protons + Number of neutrons.

Question: 4. How can you determine number of neutrons in the nucleus of an atom from the knowledge of mass number and atomic number?

Answer: The mass number of an atom is equal to the number of protons plus the number of neutrons that it contains. In other words, the number of neutrons in any atom is its mass number minus its atomic number.

Question: 5. Draw geometric representation of following atoms, showing clearly, the number of protons, number of neutrons and number of electrons in various shells.

(a) Calcium ₂₀Ca⁴⁰

Answer:

(b) Argon ₁₈Ar⁴⁰

Answer:

(c) Chlorine ₁₇Cl³⁵

Answer:

Question: 6. Define isotopes giving examples. State three properties of isotopes.

Answer: Isotopes: Elements having the same atomic number but the different mass numbers are isotopes of each other. Both forms of the element have the same number of protons. Number of neutrons is different in isotopes.

Example: ₇N¹⁴and ₇N¹⁵

Question: 7. Draw geometric diagrams of three isotopes of hydrogen.

Answer:

Question: 8. State three ways by which atomic theory of structure of matter, differs from Dalton’s atomic theory of matter.

Answer: State three ways by which atomic theory of the structure of matter differs from Daltons atomic theory of matter. According to Dalton atom is a tiny particle and is indivisible. Whereas according to atomic theory of matter atoms are divisible and is having mainly atomic forces. For these forces electrons are responsible.

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