NCERT Plus One Chemistry: Structure of an Atom Quiz

Question 1

In Rutherford’s alpha-particle scattering experiment, the observation that most alpha particles passed through the foil undeflected led directly to which conclusion?

Accepted Answer

Most of the atom is empty space

Answer

The atom has a small, dense nucleus

Answer

Electrons are embedded uniformly in positive charge

Answer

Protons and neutrons have nearly equal masses

Question 2

Which statement best explains why the line spectrum of hydrogen consists of discrete lines instead of a continuous band?

Accepted Answer

Electrons can occupy only certain allowed energy levels

Answer

Hydrogen contains only one proton in the nucleus

Answer

The atom emits all wavelengths with equal intensity

Answer

Its nucleus absorbs part of the emitted radiation

Question 3

For an electron in the Bohr model, when it moves from n = 4 to n = 2, the radiation emitted belongs to which spectral series?

Accepted Answer

Balmer series

Answer

Lyman series

Answer

Paschen series

Answer

Brackett series

Question 4

The de Broglie wavelength of a particle increases when which change occurs, assuming non-relativistic motion?

Accepted Answer

Its momentum decreases

Answer

Its kinetic energy doubles

Answer

Its speed increases sharply

Answer

Its mass and velocity both increase

Question 5

Which pair of quantum numbers is not allowed for an electron in an atom?

Accepted Answer

n = 3, l = 3

Answer

n = 3, l = 2

Answer

n = 2, l = 1

Answer

n = 4, l = 3

Question 6

If the principal quantum number n = 4, what is the maximum possible number of orbitals in that shell?

Accepted Answer

16

Answer

8

Answer

18

Answer

32

Question 7

Which statement correctly compares the 2s and 2p orbitals of a hydrogen atom?

Accepted Answer

They have different shapes but equal energies

Answer

They have equal shapes and different energies

Answer

They have equal energies only in multielectron atoms

Answer

They differ in both shape and magnetic quantum number only

Question 8

According to Heisenberg’s uncertainty principle, if the uncertainty in position of a microscopic particle decreases significantly, what happens to the uncertainty in momentum?

Accepted Answer

It increases

Answer

It becomes zero

Answer

It remains unchanged

Answer

It also decreases proportionally

Question 9

Which quantum number determines the orientation of an orbital in space?

Accepted Answer

Magnetic quantum number

Answer

Principal quantum number

Answer

Azimuthal quantum number

Answer

Spin quantum number

Question 10

How many electrons can have the quantum numbers n = 3 and l = 2 in a given atom?

Accepted Answer

10

Answer

2

Answer

6

Answer

14

Question 11

Which electronic transition in the hydrogen atom would require absorption of energy rather than emission?

Accepted Answer

n = 2 to n = 4

Answer

n = 5 to n = 2

Answer

n = 3 to n = 1

Answer

n = 4 to n = 3

Question 12

In a multielectron atom, why is the 4s orbital generally filled before the 3d orbital?

Accepted Answer

4s has lower energy than 3d in neutral atoms

Answer

4s has more possible orientations than 3d

Answer

3d is forbidden until 4s is completely paired

Answer

4s electrons are always closer to the nucleus

Question 13

Which one of the following sets of quantum numbers represents the last electron of sodium (Z = 11) in its ground state?

Accepted Answer

n = 3, l = 0, m = 0, s = +1/2

Answer

n = 3, l = 1, m = 0, s = +1/2

Answer

n = 2, l = 1, m = 0, s = -1/2

Answer

n = 3, l = 0, m = 1, s = +1/2

Question 14

The probability of finding an electron is maximum in an orbital at the region where the value of |ψ|² is:

Accepted Answer

maximum

Answer

minimum

Answer

negative

Answer

exactly zero

Question 15

Which of the following subshells can exist for n = 3?

Accepted Answer

3s, 3p, 3d

Answer

3s, 3p, 3d, 3f

Answer

Only 3s and 3p

Answer

Only 3d and 3f

Question 16

What is the maximum number of electrons that can be accommodated in all orbitals having n = 2?

Accepted Answer

8

Answer

2

Answer

6

Answer

10

Question 17

Which statement about the nodal structure of orbitals is correct?

Accepted Answer

A 2s orbital has one radial node

Answer

A 2p orbital has one radial and one angular node

Answer

A 3p orbital has no radial node

Answer

A 3d orbital has two angular nodes

Question 18

In the photoelectric effect, if the frequency of incident light is below the threshold frequency, what happens?

Accepted Answer

No electrons are emitted

Answer

Electrons are emitted with lower kinetic energy

Answer

Electrons are emitted only after a time lag

Answer

Only positively charged particles are emitted

Question 19

Which principle is violated by the electronic configuration 1s² 2s² 2p⁷?

Accepted Answer

Pauli exclusion principle

Answer

Hund’s rule

Answer

Heisenberg uncertainty principle

Answer

de Broglie relation

Question 20

For a hydrogen-like species, the radius of the orbit depends on n and Z. Which change would decrease the orbital radius most effectively?

Accepted Answer

Increasing Z while keeping n constant

Answer

Increasing n while keeping Z constant

Answer

Decreasing Z while keeping n constant

Answer

Keeping both n and Z unchanged

NCERT Plus One Chemistry: Structure of an Atom Quiz

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