Viraf J. Dalal solutions for New Simplified Middle School Chemistry [English] Class 8 chapter 4 - Atomic Structure [Latest edition]

State the main postulates of Dalton’s atomic theory.

Explain how the modern atomic theory contradicted Dalton’s atomic theory.

With reference to the discovery of the structure of an atom, explain in brief – William Crookes experiment for the discovery of cathode rays, followed by – J.J. Thomsons experiment pertaining to the constituents of the cathode rays. State which sub-atomic particle was discovered from his experiment.

Explain in brief – Goldstein’s experiment which led to the discovery of the proton.

Explain in brief – Lod Rutherford’s experiment which led to the discovery of the atomic nucleus.

‘Electrons revolve around the nucleus in fixed orbits or shells called energy levels’. State how these energy levels are represented.

Draw a neat labelled diagram representing an atom. Name the three sub-atomic particles in the atom and represent them symbolically showing the mass and charge of each. State where the sub-atomic particles are present in the atom.

Define the term ‘atomic number’ of an atom.

If an atom ‘A’ has an atomic number of eleven, state the number of protons and electrons it contains.

Define the term ‘mass number’ of an atom.

If an atom ‘A’ has mass number 35 and atomic number 17, state the number of protons, electrons and neutrons it contains.

State why the atomic weight of an element is also termed relative atomic mass.

State how electrons are distributed in an atom. Explain in brief the rules which govern their distribution.

If an atom ‘A’ has atomic number 19 and mass number 39, state –

1. Its electronic configuration.
2. The number of valence electrons it possesses.

Draw the atomic diagram of the following element showing the distribution of – protons, neutrons and the electrons in the various shell of the atom.

Carbon – $${\phantom{A}}_{\phantom{6}}^{\phantom{12}}{\phantom{A}}_{\phantom{2}6}^{\phantom{2}12}\mathrm{C}$$

[The upper number represent the – mass number and the lower number represent the – atomic number e.g. calcium – mass number = 40, atomic number = 20]

Draw the atomic diagram of the following element showing the distribution of – protons, neutrons and the electrons in the various shell of the atom.

Oxygen – $${\phantom{A}}_{\phantom{8}}^{\phantom{16}}{\phantom{A}}_{\phantom{2}8}^{\phantom{2}16}\mathrm{O}$$

[The upper number represent the – mass number and the lower number represent the – atomic number e.g. calcium – mass number = 40, atomic number = 20]

Draw the atomic diagram of the following element showing the distribution of – protons, neutrons and the electrons in the various shell of the atom.

Phosphorus – $${\phantom{A}}_{\phantom{15}}^{\phantom{31}}{\phantom{A}}_{\phantom{2}15}^{\phantom{2}31}\mathrm{P}$$

[The upper number represent the – mass number and the lower number represent the – atomic number e.g. calcium – mass number = 40, atomic number = 20]

Draw the atomic diagram of the following element showing the distribution of – protons, neutrons and the electrons in the various shell of the atom.

Argon – $${\phantom{A}}_{\phantom{18}}^{\phantom{40}}{\phantom{A}}_{\phantom{2}18}^{\phantom{2}40}\mathrm{Ar}$$

[The upper number represent the – mass number and the lower number represent the – atomic number e.g. calcium – mass number = 40, atomic number = 20]

Draw the atomic diagram of the following element showing the distribution of – protons, neutrons and the electrons in the various shell of the atom.

Calcium – $${\phantom{A}}_{\phantom{20}}^{\phantom{40}}{\phantom{A}}_{\phantom{2}20}^{\phantom{2}40}\mathrm{Ca}$$

[The upper number represent the – mass number and the lower number represent the – atomic number e.g. calcium – mass number = 40, atomic number = 20]

‘Valency is the number of hydrogen atoms which can combine with [or displace] one atom of the element [or radical] forming a compound’. With reference to the above definition of valency, state the valency of chlorine in hydrogen chloride, giving reasons.

‘Valency is also the number of electrons – donated or accepted by an atom so as to achieve the stable electronic configuration of the nearest noble gas’. With reference to this definition –
State what is meant by ‘stable electronic configuration’.

‘Valency is also the number of electrons – donated or accepted by an atom so as to achieve the stable electronic configuration of the nearest noble gas’. With reference to this definition –
State why the valency of sodium, magnesium and aluminium is: +1, +2 & +3 respectively.

‘Valency is also the number of electrons – donated or accepted by an atom so as to achieve the stable electronic configuration of the nearest noble gas’. With reference to this definition –
State why the valency of chlorine, oxygen and nitrogen is: −1, −2 and −3 respectively.

With reference to the formation of compounds from atoms by electron transfer – electron valency, state the basic steps in the conversion of sodium and chlorine atoms to sodium and chloride ions leading to the formation of the compound – sodium chloride.
[electronic configuration of: Na = 2, 8, 1 & Cl = 2, 8, 7]

Match the statements in List I with the correct answer from List II.

Select the correct answer from the choice in the bracket to complete the sentence:

An element ‘X’ has six electrons in its outer or valence shell. Its valency is __________.

Select the correct answer from the choice in the bracket to complete the sentence:

An element ‘Y’ has electronic configuration 2, 8, 6. The element ‘Y’ is a _________.

Select the correct answer from the choice in the bracket to complete the sentence:

A ________ is a sub-atomic particle with no charge and unit mass.

Select the correct answer from the choice in the bracket to complete the sentence:

An element Z with zero valency is a ________.

Select the correct answer from the choice in the bracket to complete the sentence:

Magnesium atom with electronic configuration 2, 8, 2 achieves stable electronic configuration by losing two electrons, thereby achieving stable electronic configuration of the nearest noble gas _______.

The diagram represents an isotope of hydrogen [H]. Answer the following:

Atomic no. = 1
Mass no. = 1

Are isotopes atoms of the same element or different elements.

The diagram represents an isotope of hydrogen [H]. Answer the following:

Atomic no. = 1
Mass no. = 1

Do isotopes have the same atomic number or the same mass number?

The diagram represents an isotope of hydrogen [H]. Answer the following:

Atomic no. = 1
Mass no. = 1

If an isotope of ‘H’ has mass no. = 2, how many electrons does it have.

The diagram represents an isotope of hydrogen [H]. Answer the following:

Atomic no. = 1
Mass no. = 1

If an isotope of ‘H’ has mass no. = 3, how many neutrons does it have.

The diagram represents an isotope of hydrogen [H]. Answer the following:

Atomic no. = 1
Mass no. = 1

Which sub-atomic particles in the 3 isotopes of ‘H’ are the same.

State the electronic configuration for of the following:

Hydrogen [p = 1]

State the electronic configuration for of the following:

Boron [P = 5]

State the electronic configuration for of the following:

Nitrogen [p = 7]

State the electronic configuration for of the following:

Neon [p = 10]

State the electronic configuration for of the following:

Magnesium [p = 12]

State the electronic configuration for of the following:

Aluminium [p = 13]

State the electronic configuration for of the following:

Sulphur [p = 16]

State the electronic configuration for of the following:

Argon [p = 18]

State the electronic configuration for of the following:

Potassium [p = 19]

State the electronic configuration for of the following:

Calcium [p = 20]

Draw the structure of the following atoms showing the nucleus containing – protons, neutrons and the orbits with the respective electron:

Lithium [At. no. = 3, Mass no. = 7]

Draw the structure of the following atoms showing the nucleus containing – protons, neutrons and the orbits with the respective electron:

Carbon [At. no. = 6, Mass no. = 12]

Draw the structure of the following atoms showing the nucleus containing – protons, neutrons and the orbits with the respective electron:

Silicon [At. no. = 14, Mass no. = 28]

Draw the structure of the following atoms showing the nucleus containing – protons, neutrons and the orbits with the respective electron:

Sodium [At. no. = 11, Mass no. = 23]

Draw the structure of the following atoms showing the nucleus containing – protons, neutrons and the orbits with the respective electron:

Isotopes of hydrogen [1₁H, 2₁H, 3₁H]