Question 1

Which of the following statements best describes the difference between the atomic number (Z) and the mass number (A) of an atom?

Accepted Answer

The atomic number is the number of protons, while the mass number is the sum of protons and neutrons.

Question 2

A neutral atom of sodium has an atomic number $$Z = 11$$ and a mass number $$A = 23. $$How many neutrons does it contain?

Accepted Answer

$$12$$ neutrons

Question 3

Which of the following best explains why the emission spectrum of hydrogen consists of discrete lines rather than a continuous spectrum?

Accepted Answer

Energy levels in the atom are quantized, so electrons can only occupy specific energy states.

Question 4

According to Bohr's model, what is the energy (in eV) of the electron in the $$n=2$$ orbit of a hydrogen atom?

Accepted Answer

$$-3.4 eV$$

Question 5

A photon with energy $$E = 10.2 eV is $$absorbed by a hydrogen atom in its ground state. To which energy level does the electron transition?

Accepted Answer

From $$n=1 to$$ $$n=2$$

Question 6

Calculate the wavelength (in nm) of the photon emitted when an electron in a hydrogen atom falls from $$n=3 to$$ $$n=2. $$Use $$R_H = 1.097 	imes 10^7$ m$$^{-1}$$.

Accepted Answer

$$486 nm$$

Question 7

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Azimuthal (angular momentum) quantum number $$l$$

Question 8

How many atomic orbitals are present in the $$n=3$$ shell?

Accepted Answer

$$9$$

Question 9

Which of the following statements about electron spin is correct?

Accepted Answer

Two electrons in the same orbital must have opposite spins.

Question 10

Which rule explains why electrons fill degenerate orbitals singly before pairing up?

Accepted Answer

Hund's rule

Question 11

What is the wavelength (in meters) associated with an electron moving at $$v = 1 	imes 10^6$ m/s? (h = 6.63$$ 	imes $$10^{-34} J$$·s, $$m_e = 9.1 	imes 10$$^{-31}$$ kg)

Accepted Answer

$$7.3 	imes 10$$^{-10}$$ m

Question 12

Which of the following is a correct electron configuration for the ground state of oxygen ($$Z=8$$)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^4$$

Question 13

Which of the following atoms is diamagnetic?

Accepted Answer

Neon ($$Z=10)$$

Question 14

Which of the following best describes an isotope?

Accepted Answer

Atoms with the same number of protons but different numbers of neutrons.

Question 15

The Heisenberg uncertainty principle states that:

Accepted Answer

It is impossible to know both the position and momentum of a particle with absolute precision.

Question 16

Which quantum numbers are needed to uniquely describe an electron in an atom?

Accepted Answer

$$n$$, $$l$$, $$m$$, and $$s$$

Question 17

Which of the following ions is hydrogen-like and has an ionization energy of $$217.6 eV$$?

Accepted Answer

$$^4Be$$^{3+}$$

Question 18

What is the maximum number of electrons that can occupy the $$n=2$$ shell?

Accepted Answer

$$8$$

Question 19

Which of the following best describes the Pauli exclusion principle?

Accepted Answer

No two electrons in an atom can have the same set of four quantum numbers.

Question 20

Which of the following transitions in the hydrogen atom would emit a photon with the highest energy?

Accepted Answer

From $$n=2 to$$ $$n=1$$

Structure of the Atom and Quantum Models: General Chemistry Study Notes

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