Atomic Structure

Question 1

Atomic radius is of the order of  10⁻⁸. cm and nuclear radius is of the order of  10⁻¹³ cm. Calculate what fraction of atom is occupied by nucleus?

Accepted Answer

1 × 10⁻¹⁵

Answer

1 × 10⁻²⁰

Answer

1 × 10⁻¹²

Answer

None

Question 2

Atomic weight of an element is not necessarily whole number because

Accepted Answer

it contains isotopes

Answer

it contains electrons, protons and neutrons

Answer

it contains allotropic forms

Answer

atoms are no longer considered indivisible

Question 3

Which of the following are isoelectronic with one another?

Accepted Answer

Na+ and Ne

Answer

K+ and O

Answer

Ne and O

Answer

Na+ and K+

Question 4

The mass of an atom is constituted mainly by

Accepted Answer

Neutron and proton

Answer

Neutron and neutrino

Answer

Neutron and electron

Answer

Proton and electron

Question 5

When atoms are bombarded with alpha particles, only a few in million suffer deflection, others pass out undeflected. This is because

Accepted Answer

The nucleus occupies much smaller volume compared to the volume of the atom

Answer

The force of repulsion on the moving alpha particle is small

Answer

The force of attraction on the alpha particle to the oppositely charged electrons is very small

Answer

There is only one nucleus and large number of electrons

Question 6

Photoelectric effect is maximum in:

Accepted Answer

Cs

Answer

Na

Answer

K

Answer

Li

Question 7

Which of the following electron transition in a hydrogen atom will require the largest amount of energy?

Accepted Answer

From n =  to n = 1

Answer

From n = 1 to n = 2

Answer

From n = 2 to n = 3

Answer

From n = 3 to n = 5

Question 8

Match the following
(A) Energy of ground state of He+
(i) + 6.04 eV
(B) Potential energy of I orbit of H-atom
(ii) -27.2 eV
(C) Kinetic energy of II excited state of He+
(iii) 54.4 V
(D) Ionisation potential of He+
(iv) - 54.4 eV

Accepted Answer

A- (iv), B – (ii), C – (i), D – (iii)

Answer

A- (i), B – (ii), C – (iii), D – (iv)

Answer

A- (iv), B – (iii), C – (ii), D – (i)

Answer

A – (ii), B – (iii), C – (i), D – (iv)

Question 9

Bohr's model can explain :

Accepted Answer

The spectrum of atom or ion containing one electron only

Answer

The spectrum of hydrogen atom only

Answer

The spectrum of hydrogen molecule only

Answer

The solar spectrum

Question 10

If the series limit of wavelength of the Lyman series for the hydrogen atoms is 912Å, then the series limit of wavelength for the Balmer series of the hydrogen atom is :

Accepted Answer

912 x 4 Å

Answer

912 Å

Answer

912 × 2 Å

Answer

912/2 Å

Question 11

The radius of hydrogen in ground state is 0.53 Å. In normal state the radius of Li²+ (atomic number = 3) in ground state will be :

Accepted Answer

0.17 Å

Answer

1.06 Å

Answer

0.265 Å

Answer

0.53 Å

Question 12

The transition of the electron in hydrogen atom from the fourth to first energy shell emits a spectral line which falls in following series.

Accepted Answer

Lyman

Answer

Balmer

Answer

Pashen

Answer

Bracket

Question 13

The speed of a proton is one hundredth of the speed of light in vacuum. What is its de-Broglie wavelength? Assume that one mole of protons has a mass equal to one gram [h = 6.626 × 10-27 erg sec] :

Accepted Answer

1.33 × 10-3 Å

Answer

13.31 × 10-7 Å

Answer

13.13 × 10-5 Å

Answer

1.31 × 10-2 Å

Question 14

The uncertainity in position and velocity of a particle are 10-10 m and 5.27 × 10-24 ms-1 respectively. Calculate the mass of the particle (h = 6.625 × 10-34 Joule sec.)

Accepted Answer

0.099 Kg

Answer

0.089 Kg

Answer

0.99 Kg

Answer

Can not predict

Question 15

The wavelength of a charged particle the square root of the potential difference through which it is accelerated :

Accepted Answer

is inversely proportional to

Answer

is directly proportional to

Answer

is independent of

Answer

is unrelated with

Question 16

Which of the following set of quantum numbers are permitted

Accepted Answer

n = 3, l = 2, m = − 2, s = +1/2

Answer

n = 3, l = 2, m = − 1, s = 0

Answer

n = 2, l = 2, m = +1, s = – 1/2

Answer

n = 2, l = 2, m = +1, s = – 1/2

Question 17

Magnetic quantum number specifies -

Accepted Answer

Orientation of orbitals

Answer

Size of orbitals

Answer

Shape of orbitals

Answer

Nuclear stability

Question 18

Magnetic moment of Xn+ (Z = 26) is √24 B.M. Hence number of unpaired electrons and value of n respectively are :

Accepted Answer

4, 2

Answer

2, 4

Answer

3, 1

Answer

0, 2

Question 19

Which of the following principles/rules limits the maximum number of electrons in an orbital to two

Accepted Answer

Pauli's exclusion principle

Answer

Aufbau principle

Answer

Hund's rule of maximum multiplicity

Answer

Heisenberg's uncertainty principle

Question 20

The quantum numbers for the outermost electron of an element are given below as n = 2, l = 0, m = 0, s = + 7. The atoms is :

Accepted Answer

Lithium

Answer

Beryllium

Answer

Hydrogen

Answer

Boron

Question 21

An element has the electronic configuration 1s², 2s22p6,3s23p2 . Its valency electrons are :

Question 22

If 10-17 J of light energy is needed by the interior of human eye to see an object. The number of photons of green light (λ = 550 nm) needed to see the object are:

Question 23

In a sample of H-atom electrons make transition from 5th excited state to ground state, producing all possible types of photons, then number of lines in infrared region are

Question 24

What is likely to be orbit number for a circular orbit of diameter 20 nm of the hydrogen atom if we assume Bohr orbit to be the same as that represented by the principal quantum number?

Question 25

Energy required to pull out an electron from 1st orbit of hydrogen atom to infinity is 100 units. The amount of energy needed to pull out the electron from 2nd orbit to infinity is :

Question 26

A photon of 300 nm is absorbed by a gas and then emits two photons. One photon has a wavelength 496 nm then the wavelength of second photon in nm :

Question 27

For sodium atom the number of electrons with m = 0 will be :

Question 28

The orbital angular momentum for an electron revolving in an orbit is given by √l(l+1) h/2π. This momentum for an s-electron will be given by

Question 29

The wavelength of the radiation emitted, when in a hydrogen atom electron falls from infinity to stationary state 1, would be (Rydberg constant = 1.097 × 107 m¯¹)

Question 30

The energy required to break one mole of CI-CI bonds in Cl₂ is 242 kJ mol-1. The longest wavelength of light capable of breaking a single CI-CI bond is : (c = 3 × 10º m s-¹ and NA = 6.02 × 1023 mol-1)

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