Question 1

Which statement best explains why atomic radius decreases across a period from left to right?

Accepted Answer

Effective nuclear charge increases, pulling valence electrons closer to the nucleus.

Question 2

Which of the following elements would you expect to have the highest first ionization energy?

Accepted Answer

Sulfur ($$S)$$

Question 3

What is the electron configuration for the $$Fe^{2+}$$ ion?

Accepted Answer

$$[Ar]3d^6$

Question 4

Which of the following ions is expected to be paramagnetic?

Accepted Answer

$$Fe^{3+}$$

Question 5

According to Coulomb's Law, what happens to the potential energy between two electrons as the distance between them increases?

Accepted Answer

The potential energy decreases (becomes less positive).

Question 6

Which element is more metallic: $$Ge or$$ $$P$$? Explain using periodic trends.

Accepted Answer

$$Ge is $$more metallic because metallic character increases down a group and to the left across a period.

Question 7

Which of the following statements about the periodic law is correct?

Accepted Answer

Elements are arranged by increasing atomic number, and their properties repeat periodically.

Question 8

Which orbital has the greatest penetration toward the nucleus?

Accepted Answer

$$2s$$

Question 9

A neutral atom of bromine ($$Br) $$and a $$Kr$$ atom are isoelectronic. Which is larger and why?

Accepted Answer

$$Br is $$larger because it has fewer protons, resulting in a lower effective nuclear charge.

Question 10

Which of the following elements has the most unpaired electrons in its ground-state electron configuration?

Accepted Answer

$$N$$

Question 11

What is the expected charge of an ion formed by a group 2A element, and what is its electron configuration relative to the nearest noble gas?

Accepted Answer

2+; same configuration as the previous noble gas

Question 12

Which of the following best describes Hund's rule?

Accepted Answer

Electrons occupy degenerate orbitals singly with parallel spins before pairing.

Question 13

Which element would have the most negative electron affinity?

Accepted Answer

$$Cl$$

Question 14

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

Accepted Answer

$$[Ar]4s^13$d^5$

Question 15

Which of the following best explains why the first ionization energy of $$B is $$lower than that of $$Be$$?

Accepted Answer

The electron removed from $$B is in a$$ $$2p$$ orbital, which is higher in energy and less shielded than the $$2s$$ orbital in $$Be.$$

Question 16

Which of the following is true about the density of elements as you move down a column in the periodic table?

Accepted Answer

Density generally increases because mass increases faster than volume.

Question 17

Which of the following elements is expected to be most malleable?

Accepted Answer

$$Na$$

Question 18

Which of the following statements about shielding is correct?

Accepted Answer

Core electrons shield valence electrons from the full nuclear charge.

Question 19

Which of the following ions is largest in size?

Accepted Answer

$$F^-$$

Question 20

Which of the following elements is expected to have the lowest melting point?

Accepted Answer

$$Li$$

Periodic Law and Periodic Properties of Elements

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