Question 1

Which of the following statements best describes the periodic law as established by Mendeleev?

Accepted Answer

When elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically.

Question 2

Which quantum number is associated with the orientation of an orbital in space?

Accepted Answer

Magnetic quantum number, $$m_l$$

Question 3

What is the electron configuration for a ground-state potassium (K) atom?

Accepted Answer

$$1s^22s^22$p^63s^23$p^64s^1$

Question 4

Which of the following best explains why atomic radius increases down a group in the periodic table?

Accepted Answer

The principal quantum number of the valence shell increases, placing electrons farther from the nucleus.

Question 5

Which element would you expect to have the highest first ionization energy?

Accepted Answer

Chlorine ($$Cl)$$

Question 6

Which of the following ions is isoelectronic with argon ($$Ar$$)?

Accepted Answer

$$S^{2-}$$

Question 7

Which of the following best describes Hund’s Rule?

Accepted Answer

Electrons occupy degenerate orbitals singly before pairing.

Question 8

Which of the following elements is expected to have the most metallic character?

Accepted Answer

Sodium ($$Na)$$

Question 9

Which of the following electron configurations represents a transition metal cation?

Accepted Answer

$$[Ar]4s^03$d^5$

Question 10

Which of the following best explains why the first ionization energy generally increases across a period?

Accepted Answer

The effective nuclear charge increases, pulling electrons closer to the nucleus.

Question 11

Which of the following species is paramagnetic?

Accepted Answer

$$Fe^{3+}$$

Question 12

Which of the following is the correct order of atomic radius from smallest to largest: $$O$$, $$S$$, $$Se$$?

Accepted Answer

$$O \u003c S \u003c Se$$

Question 13

Which of the following best describes the electron configuration of $$Cu as $$found experimentally?

Accepted Answer

$$[Ar]4s^13$d^{10}$

Question 14

Which of the following statements about electron affinity is correct?

Accepted Answer

Halogens have the highest (most negative) electron affinities in their periods.

Question 15

Which of the following best explains why $$S^{2-} is $$larger than $$S$$?

Accepted Answer

$$S^{2-}$$ has more electrons, increasing electron-electron repulsion and size.

Question 16

Which of the following is the correct set of quantum numbers for the last electron added to a $$Rb$$ atom ($$Z=37$$)?

Accepted Answer

$$n=5,\ l=0,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 17

Which of the following elements would be expected to form a $$2+$$ cation with a noble gas configuration?

Accepted Answer

Magnesium ($$Mg)$$

Question 18

Which of the following best describes the trend in metallic character across a period?

Accepted Answer

Metallic character decreases from left to right.

Question 19

Which of the following is the correct order of increasing first ionization energy: $$K$$, $$Ca$$, $$Sc$$?

Accepted Answer

$$K \u003c Ca \u003c Sc$$

Question 20

Which of the following best explains why the second ionization energy of sodium is much higher than the first?

Accepted Answer

The second electron is removed from a noble gas core, which is much more stable.

Periodicity and Periodic Trends: Structure, Electron Configuration, and Properties of the Elements

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