Imporant Questions Regarding 4th Unit (Atomic and Nuclear Physics)

 

1. An orbital is having n = 3 and l = 1, the number of electrons it can occupy are

(a) 6

(b) 14

(c) 10

(d) 2

2. The force that allows electrons to move around the nucleus is

(a) nuclear force

(b) weak nuclear force

(c) electrostatic force

(d) gravitational force

3. According to Bohr’s atomic model, the radius of the orbit is directly proportional to

(a) n²

(b) 1/n²

(c) 1/n

(d) n

4. According to Bohr’s atomic model, the angular momentum of orbits is multiple of

(a) h/2𝜋

(b) 2𝜋/h

(c) 2h/𝜋

(d) 𝜋/2h

5. When electrons move from a lower energy level to a higher energy level, energy is

(a) absorbed

(b) emitted

(c) both (a) and (b)

(d) none of the above

6. Radius of the hydrogen atom on going to the first excited state is _____ of Bohr’s radius.

(a) double

(b) half

(c) 4 times

(d) same

7. The energy of each orbit is

(a) same

(b) fixed

(c) changes with time

(d) none of the above

8. How many atomic orbitals are present in the fourth energy level of an atom?

(a) 32

(b) 8

(c) 16

(d) 4

9. A subshell of an atom contains a maximum of _____ electrons.

(a) 4l – 2

(b) 4l + 2

(c) 2l + 1

(d) 2n²

10. When electrons move from the higher energy level to a lower energy level, energy is

(a) absorbed

(b) emitted

(c) both (a) and (b)

(d) none of the above

Answer

1. (d)	2. (c)	3. (a)	4. (a)	5. (a)
6. (c)	7. (b)	8. (c)	9. (b)	10. (b)

 

Energy Level Diagram

Q1. What are the energy levels?

Electrons of an atom occupying particular orbitals have a particular energy. This is called energy level. When an electron alleviates from a high energy state to a lower energy state, emission of light occurs.

Q2. What is an electron shell?

The space around the nucleus which is filled will force more electrons out from the nucleus. This is called an electron shell.

Q3. What is the lowest possible energy and highest energy level of an electron?

The lowest possible energy is ground state and  highest energy level is the excited state.

Q4. How the energy levels are filled in an atom?

In the increasing order of energy according to the Aufbau principle.

Q5. What is the order of filling of energy levels within the same main energy level?

s < p < d < f

 

What is Bohr’s Model of an Atom?

Q1.  How do electrons move according to Bohr’s model?

The theory notes that electrons in atoms travel around a central nucleus in circular orbits and can only orbit stably at a distinct set of distances from the nucleus in certain fixed circular orbits. Such orbits are related to certain energies and are also referred to as energy shells or energy levels.

Q2.  How did Bohr discover electrons?

Bohr was the first to discover that electrons move around the nucleus in different orbits and that an element’s properties are determined by the number of electrons in the outer orbit.

Q3.  Did Bohr’s model have neutrons?

The nucleus in the atom’s Bohr model holds most of the atom’s mass in its protons and neutrons. The negatively charged electrons, which contribute little in terms of mass, but are electrically equivalent to the protons in the nucleus, orbit the positively charged core.

Q4.  How did Sommerfeld modify Bohr’s theory?

Many modifications have been introduced to the Bohr model, most notably the Sommerfeld model or Bohr – Sommerfeld model, which suggested that electrons move around a nucleus in elliptical orbits rather than circular orbits of the Bohr model. The Bohr – Sommerfeld system was essentially incoherent, contributing to many paradoxes.

Q5. Who discovered electrons?

J. J. Thomson in 1897 discovered Electron when he was studying the properties of the cathode ray.