Q: A 100-watt light bulb emits light at a wavelength of 525 nm. How many photons are emitted per second? ($$h = 6.626 \times 10$$^{-34}$$ J·s, c = 3.00$$ \times $$10^8 m/s)$$

$$2.64 \times 10$$^{20}$$ photons/s

Question 1

Which of the following best explains why the classical mechanical model of the atom failed to describe atomic structure accurately?

Accepted Answer

It predicted that electrons would spiral into the nucleus due to energy loss.

Question 2

Which experimental observation led to the development of the quantum mechanical model of the atom?

Accepted Answer

The unique line spectra produced by different elements.

Question 3

Which equation correctly relates the frequency ($$
u) $$and wavelength ($$\lambda) of $$electromagnetic radiation?

Accepted Answer

$$
u = c / \lambda$$

Question 4

A laser emits light with a wavelength of 500 nm. What happens to the frequency of the light if the wavelength is decreased to 400 nm, assuming the speed of light remains constant?

Accepted Answer

The frequency increases.

Question 5

Which of the following statements about the photoelectric effect is correct?

Accepted Answer

Electrons are emitted only if the light frequency exceeds a threshold value, regardless of intensity.

Question 6

Calculate the energy of a single photon with a wavelength of 600 nm. Use $$h = 6.626 	imes 10$$^{-34}$$ J·s and c = 3.00$$ 	imes $$10^8 m/s.$$

Accepted Answer

$$3.31 	imes 10$$^{-19}$$ J

Question 7

Which transition in a hydrogen atom emits light with the highest energy?

Accepted Answer

n = 3 to n = 2

Question 8

According to de Broglie’s hypothesis, what is the wavelength of an electron (mass $$9.11 	imes 10$$^{-31}$$ kg) moving at 2.00$$ 	imes $$10^6 m/s$$? ($$h = 6.626 	imes 10$$^{-34}$$ J·s)

Accepted Answer

$$3.63 	imes 10$$^{-10}$$ m

Question 9

Which statement best summarizes Heisenberg’s uncertainty principle?

Accepted Answer

Either the position or the velocity of an electron can be known exactly at the same time, but not both.

Question 10

How many orbitals are present in the n = 3 principal energy level?

Accepted Answer

9

Question 11

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

Accepted Answer

n = 2, l = 2, m_l = 0, m_s = +1/2

Question 12

What is the total number of possible values for the magnetic quantum number ($$m_l) $$when $$l = 3$$?

Accepted Answer

7

Question 13

Which of the following best describes the shape of a d-orbital?

Accepted Answer

Four-lobed

Question 14

A 100-watt light bulb emits light at a wavelength of 525 nm. How many photons are emitted per second? ($$h = 6.626 	imes 10$$^{-34}$$ J·s, c = 3.00$$ 	imes $$10^8 m/s)$$

Accepted Answer

$$2.64 	imes 10$$^{20}$$ photons/s

Question 15

Which quantum number determines the energy of an electron in a hydrogen atom?

Accepted Answer

Principal quantum number ($$n)$$

Question 16

What is the energy difference ($$\Delta E) $$for an electron transition from $$n = 4 to$$ $$n = 2 in a $$hydrogen atom? ($$k = 2.179 	imes 10$$^{-18}$$ J)

Accepted Answer

$$-4.09 	imes 10$$^{-19}$$ J

Question 17

Which of the following is a consequence of the wave-particle duality of electrons?

Accepted Answer

Electrons produce interference patterns in diffraction experiments.

Question 18

How many radial nodes are present in a 4p orbital?

Accepted Answer

2

Question 19

Which of the following best describes the probability density function $$\$$psi^2$$ for an electron in a hydrogen atom?

Accepted Answer

It gives the probability of finding the electron in a unit volume at a specific point.

Quantum-Mechanical Model of the Atom: Structure, Properties, and Spectra

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