Question 1

Which of the following statements best explains why the 3d orbital in a multi-electron atom is higher in energy than the 4s orbital?

Accepted Answer

Because the 3d orbital experiences more electron-electron repulsion and less effective nuclear charge than the 4s orbital.

Question 2

Which of the following is the correct ground-state electron configuration for a neutral nickel (Ni) atom?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^6$$ $$4s^2$$ $$3d^8$$

Question 3

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

Accepted Answer

$$K^+$$

Question 4

Which of the following elements has the highest first ionization energy?

Accepted Answer

Beryllium ($$Be)$$

Question 5

Arrange the following ions in order of increasing size: $$Ca^{2+}$$, $$K^+$$, $$Cl^-$$, $$S^{2-}.$$

Accepted Answer

$$Ca^{2+}$$ \u003c K^+ \u003c Cl^- \u003c $$S^{2-}$$

Question 6

Which of the following best describes Hund’s Rule?

Accepted Answer

Electrons occupy degenerate orbitals singly before pairing up.

Question 7

Which of the following elements is most metallic?

Accepted Answer

Tin ($$Sn)$$

Question 8

Which of the following statements about atomic radius is correct?

Accepted Answer

Atomic radius decreases from left to right across a period.

Question 9

Which of the following ions has the electron configuration $$[Ar]3d$$^{10}$$?

Accepted Answer

$$Zn^{2+}$$

Question 10

Why is the third ionization energy of beryllium ($$Be) $$much higher than the first and second?

Accepted Answer

Because the third electron is removed from a filled shell, which is more stable.

Question 11

Which of the following elements has the most negative electron affinity?

Accepted Answer

Fluorine ($$F)$$

Question 12

Which of the following best explains why cations are smaller than their parent atoms?

Accepted Answer

Cations lose electrons, reducing electron-electron repulsion and sometimes removing an entire shell.

Question 13

Which of the following atoms is paramagnetic?

Accepted Answer

Oxygen ($$O)$$

Question 14

Which of the following is the abbreviated electron configuration for barium ($$Ba$$)?

Accepted Answer

$$[Xe] 6s^2$

Question 15

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

Accepted Answer

Metallic character decreases from left to right.

Question 16

Which of the following ions is larger: $$Br^- or$$ $$Rb^+$$?

Accepted Answer

$$Br^-$$

Question 17

Which of the following elements would you expect to have the largest atomic radius?

Accepted Answer

Germanium ($$Ge)$$

Question 18

Which of the following best describes the electron configuration of $$Fe^{3+}$$?

Accepted Answer

$$[Ar] 3d^5$

Question 19

Which of the following is a consequence of 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 elements is most likely to form a $$2+$$ cation?

Accepted Answer

Magnesium ($$Mg)$$

Chapter 3: Electron Configurations and Periodic Trends

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