Question 1

Which of the following best explains why atomic radius decreases across a period from left to right in the periodic table?

Accepted Answer

The effective nuclear charge ($$Z_{eff}) $$increases, attracting electrons more strongly.

Question 2

Which electron configuration represents a ground-state atom of sulfur (S, $$Z=16$$)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^4$$

Question 3

Which of the following ions is isoelectronic with argon ($$Ar$$, $$Z=18$$)?

Accepted Answer

$$Cl^-$$

Question 4

A neutral atom of vanadium ($$V$$, $$Z=23) $$has which electron configuration in noble gas shorthand?

Accepted Answer

$$[Ar] 4s^2$ 3d^3$

Question 5

Which statement about ionization energy is correct?

Accepted Answer

Ionization energy increases across a period due to increased effective nuclear charge.

Question 6

Which element would you expect to have the highest electron affinity?

Accepted Answer

Fluorine ($$F)$$

Question 7

What is the electron configuration of the $$Br^-$$ ion?

Accepted Answer

$$[Kr]$$

Question 8

Which of the following atoms or ions is paramagnetic?

Accepted Answer

$$Fe^{3+}$$

Question 9

Why are cations generally smaller than their parent neutral atoms?

Accepted Answer

Cations lose electrons, reducing electron-electron repulsion and sometimes a shell.

Question 10

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

Accepted Answer

Metallic character decreases from left to right.

Question 11

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 12

Which of the following elements has the largest atomic radius?

Accepted Answer

Potassium ($$K)$$

Question 13

Which electron configuration corresponds to an excited state of carbon ($$C$$, $$Z=6$$)?

Accepted Answer

$$1s^2$$ $$2s^1$$ $$2p^3$$

Question 14

Which of the following best explains why halogens have high (negative) electron affinities?

Accepted Answer

Halogens have a nearly full valence shell and readily gain one electron to achieve a noble gas configuration.

Question 15

Which of the following ions has the smallest ionic radius?

Accepted Answer

$$Na^+$$

Question 16

Which element is most likely to form a $$2^+$$ cation by losing two electrons from its valence shell?

Accepted Answer

Magnesium ($$Mg)$$

Question 17

Which of the following best describes the electron configuration of $$Fe^{2+}$$?

Accepted Answer

$$[Ar] 3d^6$

Question 18

Which of the following statements about effective nuclear charge ($$Z_{eff}) is $$correct?

Accepted Answer

$$Z_{eff}$$ increases across a period due to increasing nuclear charge and poor shielding by valence electrons.

Question 19

Which of the following elements is most likely to be diamagnetic in its ground state?

Accepted Answer

Zinc ($$Zn)$$

Chapter 3: Periodic Properties of the Elements – Study Notes

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