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In Rutherford’s Alpha ray scattering experiment, the following conclusions were made from the observations. 

• Atom has a very small nucleus at the centre. 
• There is a large empty space around the nucleus. 
• The entire mass of an atom is concentrated in a very small positively charged region, which is called Nucleus.
• The electrons are distributed in the vacant space around the nucleus. 
• The electrons move in circular paths around the nucleus.

1. Number of neutrons – 4 

Number of protons – 3 

Number of electrons – 3 

2. Number of neutrons – 146 

Number of protons – 92 

Number of electrons – 92

Correct answer is (c) 1A°

Isotopes are defined as elements which have the same atomic number but different mass number e.g. hydrogen has isotopes namely.

1. Protium ₁H¹

2. Deuterium ₁H²

3. Tritium ₁H³ 

Isobars are the elements which have the same mass number but the different atomic number e.g. potassium and argon are isobars.

The outermost shell of an atom is called its valence shell. The number of electrons that an atom needs to accept, donate or share so as to form a complete outer octet (eight electrons) is called the valency of that element. So, the valency of an element can be defined as its combining capacity with other elements. The valency of an element is always a whole number.

Nuclear fission: The process in which a heavy nucleus, when bombarded with slow-moving neutrons, splits into two or more lighter nuclei accompanied with a release of the tremendous amount of energy. 

Nuclear fusion: The process in which two light nuclei combine together at very high temperature, and form a stable and a heavier nucleus and is accompanied with a release of the tremendous amount of energy.

Nuclear power plant has the enlisted components.

1. Fuel: Uranium – 235 or plutonium – 239 which undergo fission easily are used as fuels.

2. Moderator: Heavy water or rods of graphite are used as moderators. The controlling rods made of cadmium or boron steel are used to regulate the number of neutrons in the reactor.

3. Coolant: As a great amount of heat is released during this process, a coolant is also required. Liquid sodium and heavy water are generally used as coolants.

Controlled radiation is used during treatment of cancer, as they can kill cancer cells.

Cobalt-60 is used for destroying malignant cells in patients suffering from cancer.

Iodine-131 is used for studying disorders of the thyroid gland. Sodium-24 is used for examining the circulation of blood.

Energy is quantized in some systems, meaning that the system can have only certain energies and not a continuum of energies, unlike the classical case. This would be like having only certain speeds at which a car can travel because its kinetic energy can have only certain values. We also find that some forms of energy transfer take place with discrete lumps of energy. While most of us are familiar with the quantization of matter into lumps called atoms, molecules, and the like, we are less aware that energy, too, can be quantized. Some of the earliest clues about the necessity of quantum mechanics over classical physics came from the quantization of energy. 

Graphs of blackbody radiation (from an ideal radiator) at three different radiator temperatures. The intensity or rate of radiation emission increases dramatically with temperature, and the peak of the spectrum shifts toward the visible and ultraviolet parts of the spectrum. The shape of the spectrum cannot be described with classical physics.

(a) 3s

n= 3, 1 = 0, m- 0

(b) 4p_z 

_n = 4, l= 1, m = 0

(c) 4d_{x² - y²}

n = 4, l = 2, m = -2 or +2

(d) 5dz₂

n = 5, l = 2, m = 0

( d) The p orbital is p_s.

Correct option  (a) (b) (c)

Explanation:

(a)  ₂₄Cr =1s²,2s² _,2p⁶,3s², 3p⁶ ,3d⁵,4s¹,

= [Ar] 3d⁵, 4s¹.

(b) For magnetic quantum number (m) negative values are possible.

For s-sub-shell : l = 0, hence m = 0

For p-sub-shell : I = 1, hence m = - 1, 0, + 1

(c)   ₄₇Ag = 1s²,2s², 2p⁶,3s², 3p⁶,3d¹⁰,4s², 4p⁶ 4d¹⁰, 5s¹

Hence, 23 electrons have a spin of one type and,24 of the opposite type.

(d) Oxidation state of N in HN₃ is -1/3.

CORRECT ANSWERS ---->

OPTION (A) since Chromium attains the given electronic configuration to attain the stability in its ground state.

OPTION (B) if l = 1 , then m = (-1,0,1) ; l = 2 , m = (-2,-1,0,1,2) and so on.

OPTION (C) since E.C. of Silver ----> [Kr]4d¹⁰5s¹

The correct answer is 

(ii) h/4π 

(d)The no nodal plane is dz²

(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 protons 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.

(c) Nucleons: The protons and neutrons collectively are known as nucleons.

(d) Valence Shell: The outermost shell of an atom is known as its valence shell.

Salient features of Dalton’s atomic theory:

1. Matter consists of very small and indivisible particles called atoms, which can neither be created nor can be destroyed. 

2. The atoms of an element are alike in all respects i.e. size, mass, density, chemical properties but they differ from the atoms of other elements. 

3. Atoms of an element combine in small numbers to form molecules of the element.

4. Atoms of one element combine with atoms of another element in simple whole number ratio to form molecules of compounds. 

5. Atoms are the smallest units of matter that can take part in a chemical reaction during which the only rearrangement of atoms takes place.

(a) According to Rutherford’s model an atom consists of:

1. The centrally located nucleus: The nucleus is a centrally located positively charged mass. The entire mass of the atom is concentrated in it. It is the densest part of the atom. Its size is very small as compare to the atom as a whole.

2. The outer circular orbits: Electrons revolve in circular orbits (shell) in the space available around the nucleus. An atom is electrically neutral i.e., the number of protons and electrons present in an atom are equal.

(b) Rutherford’s atomic model could not explain the stability of the atom as it is like a solar system, the sun is at the center and the planets revolve around it, in an atom the electrons revolve around the centrally located nucleus containing protons.

Following were the observations made by Rutherford:

1. Most of the alpha particle passed straight through the foil without any deflection from their path.

2. A small fraction of them was deflected from their original path by small angles.

3. Only a few particles bounced back.

Variable valency: Some elements exhibit more than one valence. They are said to have variable valency, e.g. Iron, copper, tin, lead.

Iron Fe     Fe²⁺ or Fe³⁺

Copper cu     cu⁺ or cu²⁺

The maximum possible number of electrons that a shell can accommodate can be given by the formula 2nr.

(Here n is the number of shells)

In case of L shell n = 2

∴ 2n² = 2(2) ² = 8

Thus L shell can accommodate a maximum number of 8 electrons.

Bohr’s Postulates:

1. The extra-nuclear region of an atom consists of electrons revolving in particular orbits called shells.

2. Each shell has a fixed energy level.

3. As long as an electron revolves in the same shell, the energy remains constant. During the electronic transition, energy is either released or absorbed.

Bohr corrected Rutherford’s model by suggesting the concepts of energy levels and electronic transition.

r_n = r₁ x n² = 0.529 x 5² = 13.225 A = 1.3225 nm

(a) 25 protons and 30 neutrons

The atomic number of chromium Cr = 24.
The electronic configuration is 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹, 3d⁵.

The radial nodes = n – l – 1
In 3s orbital n = 3, l = 0,
3s orbitals radial nodes = 3 – 0 – 1 = 2
2p orbital n = 2, l = 1,
Radial nodes of 2p orbital = 2 – 1 – 1 = 0,
Number of radial nodes of 3s and 2p orbital is 2, 0.

(a) Zero, 

(b) One spherical node,

(c) One angular node, 

(d) Two angular node.

(ii) Q-10 chlorine exits in two isotropic form cl-37, and cl-35.but its atomic mass is 35.5.This indicates the ratio of cl-37 and cl-35 is a

Correct answer is (b) 10⁹ m

Correct asnwer is (a) 10⁹

1. Oxygen, Symbol – O. 

2. Helium, Mass no. 4 Potassium, Atomic number: 19. 

3. Phosphorous, No. of Protons : 15. 

4. Carbon, Mass number: 12.

(a) No. of subshells in a shell = no. of shells = 3

(b) No. of orbitals = (no. of shell)² = 3² = 9

The answer is (D) helium

Isobars: Atoms of different elements having the same mass number, but different atomic numbers are known as isobars. 

For example: Calcium and argon have the same mass number 40, but different atomic numbers 20 and 18, respectively.

The number of atoms present in one molecule of an element or a compound is known as its atomicity.

The answer is (D) Chadwick 10^-8 cm

The answer is (A) 8p + 8n ; 8p + 9n

The answer is (A) 18 protons, 18 electrons, 22 neutrons

The answer is (D) 10^-8 cm

Isotopes: Atoms of the same element having the same atomic number but different mass numbers are called isotopes. 

For example: Chlorine has two isotopes

³⁵Cl and ³⁷₁₇Cl, in which atomic number is 17 for both, but mass numbers are 35 and 37 respectively.

Initially, 1/16th of the mass of naturally occurring oxygen was taken as the atomic mass unit because this unit gave masses of most of the elements as whole numbers.