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

The effective nuclear charge ($$Z_{\text{eff}}) $$increases, drawing the valence electrons closer to the nucleus.

Q: Which of the following is the correct order of increasing atomic radius for the elements carbon ($$\text{C}$$), nitrogen ($$\text{N}$$), and oxygen ($$\text{O}$$)?

$$\text{O} \u003c \text{N} \u003c \text{C}$$

Q: Which of the following best describes the trend in electron affinity across a period?

Electron affinity increases from left to right as $$Z_{\text{eff}}$$ increases.

Question 1

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

Accepted Answer

The effective nuclear charge ($$Z_{	ext{eff}}) $$increases, drawing the valence electrons closer to the nucleus.

Question 2

Which element would you expect to have chemical properties most similar to chlorine?

Accepted Answer

Fluorine

Question 3

According to the Aufbau principle, which orbital will the next electron occupy in a nitrogen atom after the 1s and 2s orbitals are filled?

Accepted Answer

2p orbital

Question 4

Which of the following electron configurations represents a paramagnetic atom?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^4$$

Question 5

Which of the following is the correct electron configuration for a $$	ext{Fe}^{2+}$$ ion?

Accepted Answer

$$[Ar]\ 3d^6$

Question 6

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

Accepted Answer

Magnesium ($$	ext{Mg})$$

Question 7

What is the main reason for the anomalous electron configurations of chromium ($$	ext{Cr}) $$and copper ($$	ext{Cu}$$)?

Accepted Answer

Half-filled and fully filled subshells are more stable.

Question 8

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

Accepted Answer

$$	ext{K}^+$$

Question 9

Which of the following best describes the trend in metallic character across a period from left to right?

Accepted Answer

Metallic character decreases as effective nuclear charge increases.

Question 10

Which of the following elements is classified as a metalloid?

Accepted Answer

Astatine ($$	ext{At})$$

Question 11

Which equation correctly represents the effective nuclear charge ($$Z_{	ext{eff}}) $$experienced by an electron?

Accepted Answer

$$Z_{	ext{eff}} = Z - S$$

Question 12

Which of the following statements about ionization energy is correct?

Accepted Answer

Ionization energy increases from left to right across a period.

Question 13

Which of the following ions has the largest ionic radius in the isoelectronic series: $$	ext{K}^+$$, $$	ext{Ar}$$, $$	ext{Cl}^-$$, $$	ext{S}^{2-}$$, $$	ext{P}^{3-}$$?

Accepted Answer

$$	ext{P}^{3-}$$

Question 14

Which principle states that no two electrons in an atom can have the same four quantum numbers?

Accepted Answer

Pauli Exclusion Principle

Question 15

Which of the following best explains why the second ionization energy of sodium ($$	ext{Na}) is $$much higher than the first?

Accepted Answer

The second electron is removed from a core shell, which is closer to the nucleus and experiences a higher $$Z_{	ext{eff}}.$$

Question 16

Which of the following elements has a completely filled p subshell in its ground state?

Accepted Answer

Neon ($$	ext{Ne})$$

Question 17

Which of the following best describes the electron configuration of potassium ($$	ext{K}$$)?

Accepted Answer

$$[Ar]\ 4s^1$

Question 18

Which of the following is the correct order of increasing atomic radius for the elements carbon ($$	ext{C}$$), nitrogen ($$	ext{N}$$), and oxygen ($$	ext{O}$$)?

Accepted Answer

$$	ext{O} \u003c 	ext{N} \u003c 	ext{C}$$

Question 19

Which of the following best describes the trend in electron affinity across a period?

Accepted Answer

Electron affinity increases from left to right as $$Z_{	ext{eff}}$$ increases.

Question 20

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

Accepted Answer

Cations have fewer electrons, resulting in reduced electron-electron repulsion and a smaller radius.

Periodic Trends and Electron Configurations: General Chemistry Study Notes

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