Q: Given the formula mass of $$Mg(NO_3$)_2 is 148.313 u$$, what is the percent by mass of magnesium in $$Mg(NO_3$)_2$$?

$$\frac{24.305}{148.313} \times 100\% = 16.39\%$$

Q: Which of the following is the correct formula for calculating the percent composition of an element in a compound?

$$\text{Percent composition} = \frac{\text{mass of element in 1 mole}}{\text{molar mass of compound}} \times 100\%$$

Question 1

Which property of the elements is illustrated by the periodic peaks in atomic volume for Li, Na, K, Rb, and Cs in the graph provided?

Accepted Answer

The periodic law, which states that properties recur periodically when elements are arranged by increasing atomic number.

Question 2

Based on the periodic table trends, which element would have the largest atomic radius: Se, Ba, or Sr?

Accepted Answer

Ba

Question 3

Which equation correctly represents the relationship between effective nuclear charge ($$Z_{	ext{eff}}$$), atomic number ($$Z$$), and shielding constant ($$S$$)?

Accepted Answer

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

Question 4

Which of the following ions is smallest in size: $$K^+$$, $$Cl^-$$, $$S^{2-}$$, or $$Ca^{2+}$$? All are isoelectronic.

Accepted Answer

$$Ca^{2+}$$

Question 5

Which element in the third period has the highest first ionization energy?

Accepted Answer

Ar

Question 6

What is the correct order of increasing first ionization energy for the elements As, Sn, Br, Sr?

Accepted Answer

Sr \u003c Sn \u003c As \u003c Br

Question 7

Which of the following atoms or ions is paramagnetic?

Accepted Answer

Na atom

Question 8

Which property increases as you move down a group in the periodic table?

Accepted Answer

Atomic radius and polarizability

Question 9

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

Accepted Answer

Cations are smaller than the atoms from which they are formed.

Question 10

Given the formula mass of $$Mg(NO_3$)_2 is 148.313 u$$, what is the percent by mass of magnesium in $$Mg(NO_3$)_2$$?

Accepted Answer

$$\frac{24.305}{148.313} 	imes 100\% = 16.39\%$$

Question 11

Which of the following elements would be expected to have the greatest polarizability?

Accepted Answer

Cs

Question 12

Which of the following is the correct electron configuration for $$Fe^{3+}$$?

Accepted Answer

[Ar] $$3d^5$$

Question 13

Which of the following compounds is an example of an empirical formula?

Accepted Answer

CH$$_2O$$

Question 14

If an atom has all electrons paired, what is its magnetic property?

Accepted Answer

Diamagnetic

Question 15

Which of the following elements is most likely to form a cation with a noble-gas electron configuration?

Accepted Answer

Na

Question 16

What is the formula mass of $$MgCl_2$$?

Accepted Answer

95.21 u

Question 17

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

Accepted Answer

Cs

Question 18

Which of the following statements about electron affinity is correct?

Accepted Answer

The second electron affinity is positive due to repulsion between the electron and the ion.

Question 19

Which of the following is the correct order of increasing atomic radius: F, Cl, Br, I?

Accepted Answer

F \u003c Cl \u003c Br \u003c I

Question 20

Which of the following is the correct formula for calculating the percent composition of an element in a compound?

Accepted Answer

$$	ext{Percent composition} = \frac{	ext{mass of element in 1 mole}}{	ext{molar mass of compound}} 	imes 100\%$$

The Periodic Table and Atomic Properties: Structure, Trends, and Chemical Compounds

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