Question 1

Which statement best explains why the Bohr model successfully describes the hydrogen atom's line spectrum but fails for multi-electron atoms?

Accepted Answer

The Bohr model assumes electrons occupy quantized energy levels, but ignores the effects of electron shielding in multi-electron atoms.

Question 2

According to de Broglie's hypothesis, what is the wavelength $$\lambda of an $$electron with mass $$m$$ moving at velocity $$u$$?

Accepted Answer

$$\lambda = h / (m u)$$

Question 3

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number $$l$$

Question 4

How many possible values of the magnetic quantum number $$m_l$$ are there for a $$d$$ orbital?

Accepted Answer

5

Question 5

Which of the following sets of quantum numbers is NOT allowed for an electron in an atom?

Accepted Answer

$$n=3,\ l=0,\ m_l=-1$$

Question 6

What is the maximum number of electrons that can occupy the $$3p$$ subshell?

Accepted Answer

6

Question 7

Which principle states that no two electrons in an atom can have the same set of four quantum numbers?

Accepted Answer

Pauli exclusion principle

Question 8

What is the condensed electron configuration for argon ($$Z=18$$)?

Accepted Answer

$$[Ne]3s^2$ 3p^6$

Question 9

Which element has the electron configuration $$[Ar]4s^2$ 3d$$^{10}$$ 4p^3$?

Accepted Answer

Arsenic (As)

Question 10

Why are alkali metals strong reducing agents?

Accepted Answer

They have a single $$ns^1$$ valence electron that is easily lost.

Question 11

Which orbital type has a cloverleaf shape?

Accepted Answer

$$d$$ orbital

Question 12

What is the effect of electron shielding in multi-electron atoms?

Accepted Answer

It decreases the effective nuclear charge felt by outer electrons.

Question 13

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

Accepted Answer

Hund's rule

Question 14

If an atom has the electron configuration $$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^4$$, how many valence electrons does it have?

Accepted Answer

4

Question 15

Which quantum number is responsible for the orientation of an orbital in space?

Accepted Answer

Magnetic quantum number $$m_l$$

Question 16

What is the maximum number of electrons that can occupy a single orbital?

Accepted Answer

2

Question 17

Which of the following best describes the electron configuration of a halogen?

Accepted Answer

Seven valence electrons: two in an $$s$$ orbital and five in $$p$$ orbitals.

Question 18

Which quantum number can have values of $$+\frac{1}{2} or$$ $$-\frac{1}{2}$$?

Accepted Answer

Spin quantum number $$m_s$$

Question 19

A potassium ion ($$K^+) $$emits light when heated. What determines the color of the emitted light?

Accepted Answer

The spacing between the electron energy levels in the ion.

Question 20

Which of the following statements about periodicity is correct?

Accepted Answer

Elemental properties are periodic because valence electron configurations are periodic.

Quantum Mechanics, Electron Configurations, and Periodicity: Study Notes

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