Question 1

Which principle explains why electrons fill the lowest available energy orbitals first when building up the ground-state electron configuration of an atom?

Accepted Answer

Aufbau principle

Question 2

What is the correct ground-state electron configuration for a neutral phosphorus (P, Z=15) atom?

Accepted Answer

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

Question 3

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

Accepted Answer

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

Question 4

Which rule states that electrons will occupy degenerate orbitals singly before pairing up?

Accepted Answer

Hund's rule

Question 5

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

Accepted Answer

$$[Ar]\ 3d^6$

Question 6

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

Accepted Answer

Cl$$^-$$

Question 7

Which element has the following ground-state electron configuration: $$[Ne]\ 3s^2$\ 3p^4$?

Accepted Answer

Sulfur (S)

Question 8

Why are cations generally smaller than their parent atoms?

Accepted Answer

Cations have more protons than electrons, increasing nuclear attraction and decreasing size.

Question 9

Which of the following ions is expected to be the largest in size: K$$^+$$, S$$^{2-}$$, or Cl$$^-$$?

Accepted Answer

S$$^{2-}$$

Question 10

Which of the following substances is expected to be paramagnetic?

Accepted Answer

O$$_2$$

Question 11

What is the correct electron configuration for the Ga$$^{3+}$$ ion?

Accepted Answer

$$[Ar]\ 3d$$^{10}$$

Question 12

Which of the following best explains why the Aufbau principle fails for f-block elements?

Accepted Answer

The energy difference between f and d orbitals is very small, leading to irregular filling.

Question 13

Which of the following is the correct orbital diagram for a nitrogen (N) atom?

Accepted Answer

1s: ↑↓  2s: ↑↓  2p: ↑ ↑ ↑

Question 14

Which of the following statements about the periodic table and electron configurations is correct?

Accepted Answer

Elements in the same group have similar valence electron configurations.

Question 15

Which of the following ions has the same electron configuration as a noble gas?

Accepted Answer

O$$^{2-}$$

Question 16

A sample of CrO$$_2$$ was used in magnetic tapes. What is the expected magnetic behavior of the Cr$$^{4+}$$ ion in CrO$$_2$$?

Accepted Answer

Paramagnetic, because there are unpaired electrons

Question 17

Which of the following best describes the electron configuration of a chloride ion (Cl$$^-$$)?

Accepted Answer

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

Question 18

Which of the following elements has a partially filled d subshell in its ground state?

Accepted Answer

Copper (Cu)

Question 19

Which of the following is the correct order of filling for the following orbitals according to the diagram provided: 4s, 3d, 4p?

Accepted Answer

4s → 3d → 4p

Question 20

Which of the following best explains why anions are larger than their parent atoms?

Accepted Answer

Anions have more electrons, increasing electron-electron repulsion and expanding the electron cloud.

Lec 6 notes chem

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