Question 1

Which of the following best explains why atomic radii increase as you move down a group in the periodic table?

Accepted Answer

The highest principal quantum number $$n$$ increases, so valence electrons occupy larger orbitals.

Question 2

What is the condensed electron configuration for Selenium (Se)?

Accepted Answer

$$[Ar] 4s^2$ 3d$$^{10}$$ 4p^4$

Question 3

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

Accepted Answer

Magnesium (Mg)

Question 4

Why are cations smaller than their parent atoms?

Accepted Answer

Cations have fewer electrons, so the remaining electrons experience a greater effective nuclear charge.

Question 5

Which of the following is true about the effective nuclear charge ($$Z_{eff}) $$experienced by valence electrons?

Accepted Answer

$$Z_{eff} is $$reduced by shielding from core electrons.

Question 6

Which of the following species is largest in size?

Accepted Answer

$$S^{2-}$$

Question 7

What is the main reason for the lanthanide contraction observed in the third row of transition metals?

Accepted Answer

The addition of electrons to the 4f sublevel, which do not shield the nuclear charge effectively.

Question 8

Which element has the greatest metallic character?

Accepted Answer

Sodium (Na)

Question 9

Which of the following statements about electron affinity is correct?

Accepted Answer

Group 15 elements have lower electron affinity than Group 14 due to electron pairing repulsion.

Question 10

Which of the following elements will form a $$2^+$$ cation to achieve a noble gas configuration?

Accepted Answer

Magnesium (Mg)

Question 11

What is the effective nuclear charge ($$Z_{eff}) $$experienced by the outermost electrons of carbon?

Accepted Answer

$$+4$$

Question 12

Which of the following is an exception to the expected electron configuration due to closely spaced energy levels?

Accepted Answer

Chromium: $$[Ar] 4s^1$ 3d^5$

Question 13

Which of the following groups contains elements that typically gain electrons to form stable anions?

Accepted Answer

Group 17 (halogens)

Question 14

Which of the following best describes the trend in atomic radius across a period?

Accepted Answer

Atomic radius decreases due to increasing effective nuclear charge.

Question 15

Which of the following elements has the smallest atomic radius?

Accepted Answer

Neon (Ne)

Question 16

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

Accepted Answer

$$K^+$$

Question 17

Why does the atomic radius of transition metals remain roughly constant across a period?

Accepted Answer

Electrons are added to inner $$d$$ orbitals, which do not shield effectively, so the effective nuclear charge remains similar.

Question 18

Which of the following best describes the difference between core and valence electrons?

Accepted Answer

Valence electrons are those involved in chemical bonding, while core electrons are in complete energy levels and sublevels.

Question 19

Which of the following elements is most likely to form a $$3^-$$ anion?

Accepted Answer

Nitrogen (N)

Chapter 8: Periodic Properties of the Elements – CHEM 1000 Study Notes

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