MCQs of Atoms

Atoms MCQs

Showing 71 to 80 out of 146 Questions

71.

The total energy of electron in the second excited state is -2 E. What is its potential energy in the same state with proper sign ?

(a)	-2E
(b)	-4E
(c)	4E
(d)	-E

72.

The atomic mass number of an element is _____

(a)	Always greater than its atomic number
(b)	Always smaller than its atomic number
(c)	Equal to or greater than its atomic number
(d)	Greater than its atomic number in some cases and smaller in other cases

73.

The wavelength of the first line of Lyman series for hydrogen atom is equal to that of the second line of Balmer series for a hydrogen like ion. The atomic number Z of the hydrogen like ion is _____ .

(a)	2
(b)	3
(c)	4
(d)	1

74.

An electron in the hydrogen atom jumps from excited state n to ground state. The wavelength so emitted illuminate a photosensitive material having work function 2.75 eV. If the stopping potential of the photoelectron is 10 V, then the value of n is _____

(a)	2
(b)	3
(c)	4
(d)	5

75.

An α-particle of 10 MeV is moving forward for a head on collision. What will be the distance of closest approach from the nucleus of atomic number Z = 50 ?

(a)	1.44 × 10^-14 m
(b)	2.88 × 10^-14 m
(c)	0.53 × 10^-10 m
(d)	$\frac{0.53 \times 10^{- 10}}{50} m$

76.

If the potential energy of electron in the hydrogen atom is

\frac{- e^{2}}{4 {πε}_{0} r}

, then what is its kinetic energy ?

(a)	$\frac{- e^{2}}{4 {πε}_{0} r}$
(b)	$\frac{e^{2}}{8 {πε}_{0} r}$
(c)	$- \frac{e^{2}}{8 {πε}_{0} r}$
(d)	$\frac{e^{2}}{4 {πε}_{0} r}$

77.

According to Bohr's hypothesis, the angular momentum of an electron in any stationary orbit of radius r is proportional to _____

(a)	r
(b)	$\frac{1}{r}$
(c)	$\sqrt{r}$
(d)	$r^{2}$

78.

The first Bohr radius is _____.

(a)	0·53 Å
(b)	0·25 Å
(c)	1 Å
(d)	100 Å

79.

What is the angular momentum of an electron of Li-atom in n = 5 orbit _____ .

(a)	5.27× 10^-34 Js
(b)	6.625× 10^-34 Js
(c)	1.325× 10^-34 Js
(d)	16.56× 10^-34 Js

80.

In a hydrogen like atom, the radiation emitted is found to be in ultraviolet region due to transition between n = 4 to n = 3. During which of the following transitions will the light emitted be in the infrared region ?

(a)	2 → 1
(b)	3 → 2
(c)	4 → 2
(d)	5 → 4

Showing 71 to 80 out of 146 Questions