Kaplan MCAT General Chemistry Review

—The nonmetals, located in the upper right side of the periodic table, including hydrogen, carbon, oxygen, nitrogen, and phosphorus, among others

—The metalloids or semimetals, located in a staircase formation between the metals and nonmetals, with qualities and behaviors that are combinations of those of the metals and nonmetals

The alkali and alkaline earth metals are the most reactive of all metals; they exist only in their ionic forms, having given up one or two electrons, respectively, in order to achieve the electronic configuration of the prior noble gas. The transition metals are less reactive, and many can have two or more oxidation states.

The halogens are very reactive nonmetals and are highly electronegative. They need only one electron to complete their octets and are naturally found only in the anionic state. The noble gases are the least reactive of all the elements because they have the stable octet in their valence shell. They have very high ionization energies and virtually nonexistent electronegativities.

Practice Questions

1. Lithium and sodium have similar chemical properties. For example, both can form ionic bonds with chloride. Which of the following best explains this similarity?

A. Both lithium and sodium ions are positively charged.

B. Lithium and sodium are in the same group of the periodic table.

C. Lithium and sodium are in the same period of the periodic table.

D. Both lithium and sodium have low atomic weights.

2. Carbon and silicon, elements used as the basis of biological life and synthetic computing, respectively, have some similar chemical properties. Which of the following describes a difference between the two elements?

A. Carbon has a smaller atomic radius than silicon.

B. Silicon has a smaller atomic radius than carbon.

C. Carbon has fewer valence electrons than silicon.

D. Silicon has fewer valence electrons than carbon.

3. What determines the length of an element’s atomic radius?

I. The number of valence electrons

II. The number of electron shells

III. The number of neutrons in the nucleus

A. I only

B. II only

C. I and II only

D. I, II, and III

4. Ionization energy contributes to an atom’s chemical reactivity. An accurate ordering of ionization energies, from lowest ionization energy to highest ionization energy, would be

A. Be, first ionization energy < Be, second ionization energy < Li, first ionization energy.

B. Be, second ionization energy < Be, first ionization energy < Li, first ionization energy.

C. Li, first ionization energy < Be, first ionization energy < Be, second ionization energy.

D. Li, first ionization energy < Be, second ionization energy < Be, first ionization energy.

5. Selenium is often an active component of treatments for scalp dermatitis. What type of element is selenium?

A. Metal

B. Metalloid

C. Halogen

D. Nonmetal

6. The properties of atoms can be predicted, to some extent, by their location within the periodic table. Which property or properties increase in the direction of the arrows shown?

I. Electronegativity

II. Atomic radius

III. First ionization energy

A. I only

B. II only

C. I and III only

D. II and III only

7. Metals are often used for making wires that conduct electricity. Which of the following properties of metals explains why?

A. Metals are malleable.

B. Metals have high electronegativities.

C. Metals have valence electrons that can move freely.

D. Metals have high melting points.

8. Which of the following is an important property of the set of elements shaded in the periodic table shown?

A. These elements are the best electrical conductors in the periodic table.

B. These elements form divalent cations.

C. The second ionization energy for these elements is lower than the first ionization energy.

D. The atomic radii of these elements decrease as one moves down the column.

9. When dissolved in water, which of the following ions is most likely to form a complex ion with H₂O?

A. Na⁺

B. Fe²⁺

C. Cl^-

D. S^2-

10. How many valence electrons are present in elements in the third period?

A. 2

B. 3

C. The number decreases as the atomic number increases.

D. The number increases as the atomic number increases.

11. Which of the following elements has the highest electronegativity?

A. Mg

B. Cl

C. Zn

D. I

12. Of the four atoms depicted here, which has the highest electron affinity?

13. Which of the following is true of an atom with a large atomic radius?

A. The atom is most likely to be on the right side of the periodic table.

B. The atom is likely to have a high second ionization energy.

C. The atom is likely to have low electronegativity.

D. The atom is likely to form ionic bonds.

14. Which of the following atoms/ions has the largest effective nuclear charge?

A. Cl

B. Cl^-

C. K

D. K⁺

15. Why do halogens often form ionic bonds with alkaline earth metals?

A. The alkaline earth metals have much higher electron affinities than the halogens.

B. By sharing electrons equally, the alkaline earth metals and halogens both form full octets.