Q: The effective nuclear charge ($$Z_{\text{eff}}) $$experienced by a valence electron in a sodium atom can be estimated using the formula $$Z_{\text{eff}} = Z - S. If $$sodium has 11 protons and 10 core electrons, what is the approximate $$Z_{\text{eff}}$$ for its valence electron?

$$Z_{\text{eff}} = 11 - 10 = 1$$

Question 1

Which of the following best explains why Mendeleev's periodic table was considered superior to previous attempts at organizing the elements?

Accepted Answer

He left gaps for undiscovered elements and predicted their properties accurately.

Question 2

The effective nuclear charge ($$Z_{	ext{eff}}) $$experienced by a valence electron in a sodium atom can be estimated using the formula $$Z_{	ext{eff}} = Z - S. If $$sodium has 11 protons and 10 core electrons, what is the approximate $$Z_{	ext{eff}}$$ for its valence electron?

Accepted Answer

$$Z_{	ext{eff}} = 11 - 10 = 1$$

Question 3

Which of the following correctly describes the trend in atomic radius across a period from left to right?

Accepted Answer

Atomic radius decreases due to increasing effective nuclear charge.

Question 4

Arrange the following atoms in order of increasing atomic size: B, C, Al, Si.

Accepted Answer

C \u003c B \u003c Al \u003c Si

Question 5

Which of the following statements about cations and anions is correct?

Accepted Answer

Cations are smaller and anions are larger than their parent atoms.

Question 6

In an isoelectronic series, which ion will have the smallest radius?

Accepted Answer

The ion with the largest positive charge.

Question 7

Which of the following best describes the trend in first ionization energy as you move down a group in the periodic table?

Accepted Answer

It decreases because valence electrons are farther from the nucleus.

Question 8

Which element would you expect to have the highest first ionization energy among the following: Ne, Na, P, Ar, K?

Accepted Answer

Ar

Question 9

Which of the following reactions represents the process of electron affinity for a chlorine atom?

Accepted Answer

$$\mathrm{Cl}(g) + e^- \rightarrow \mathrm{Cl}^-(g)$$

Question 10

Which of the following best explains why noble gases have positive electron affinities?

Accepted Answer

They have completely filled s and p sub-shells, making it energetically unfavorable to add an electron.

Question 11

Which of the following is a property of metals but not of nonmetals?

Accepted Answer

Good conductors of heat and electricity.

Question 12

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

Accepted Answer

Metallic character decreases.

Question 13

Which of the following statements about alkali metals (Group 1A) is correct?

Accepted Answer

They react vigorously with water to form hydroxides and hydrogen gas.

Question 14

Which of the following best explains why the reaction of potassium with water is more vigorous than that of lithium with water?

Accepted Answer

Potassium's valence electron is farther from the nucleus and more easily lost.

Question 15

Which of the following is a correct statement about the chemistry of the halogens (Group 7A)?

Accepted Answer

They have large, negative electron affinities and tend to oxidize other elements.

Question 16

Which of the following best describes the trend in reactivity of alkaline earth metals (Group 2A) with water as you move down the group?

Accepted Answer

Reactivity increases down the group.

Question 17

Which of the following is a correct statement about the oxygen group (Group 6A)?

Accepted Answer

Oxygen is a stronger oxidizer than sulfur.

Question 18

Which of the following best explains why transition metals often have variable oxidation states?

Accepted Answer

Their s and d electrons are close in energy, allowing for the loss of different numbers of electrons.

Question 19

Which of the following is a correct real-world application of a periodic trend?

Accepted Answer

Chlorine is used to disinfect water because it is a strong oxidizer due to its high electron affinity.

Chapter 7: Periodic Properties of the Elements - Comprehensive Study Notes

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