21) The number of atoms coming out of a chemical reaction must equal the number of atoms going into a chemical reaction. This follows the principle of:

A) the law of conservation of energy.

B) chemical bonding.

C) atomic theory.

D) the law of conservation of mass.

22) Which of the following is true of chemical bonds?

A) Atoms can achieve a higher energy state and less stability by forming bonds.

B) Electrons are always shared.

C) Electrons can be shared or completely transferred.

D) Chemical bonds cannot occur between two identical atoms.

23) Atoms form bonds to:

A) fill their outer shells with neutrons.

B) obtain an equal number of protons and electrons.

C) fill their outer shells with electrons.

D) fill their outer shells with protons.

E) obtain an equal number of protons and neutrons.

24) Two hydrogen atoms (atomic number 1) form a covalent bond. Which of the following is true?

A) Both hydrogen atoms now have two electrons in their outer shell.

B) Both hydrogen atoms now have two protons in their outer shell.

C) One hydrogen atom now has zero protons in its outer shell, and the other has two.

D) One hydrogen atom now has zero electrons in its outer shell, and the other has two.

E) Each hydrogen atom still has one electron in its outer shell.

25) Oxygen has six electrons in its second outer shell, and hydrogen has one. With how many hydrogen atoms will oxygen form covalent bonds?

A) eight

B) one

C) two

D) six

E) three

26) Which of the following would form the fewest covalent bonds?

A) neon (eight electrons in the second shell)

B) carbon (four electrons in the second shell)

C) hydrogen (one electron in the first shell)

D) oxygen (six electrons in the second shell)

27) Water is a polar molecule because:

A) oxygen is more electronegative than hydrogen.

B) hydrogen has more neutrons than oxygen.

C) oxygen has more electrons than hydrogen.

D) oxygen has more neutrons than hydrogen.

E) hydrogen is more electronegative than oxygen.

28) What is the difference between an ionic and covalent bond?

A) In an ionic bond, one atom accepts electrons from the other; in a covalent bond, a pair of atoms share electrons.

B) In an ionic bond, one atom has more electronegativity than the other; in a covalent bond, the atoms have the same electronegativity.

C) Ionic bonding involves the inner electron shells; covalent bonding involves the valence electron shell.

D) Ionic bonds form between atoms of different elements; covalent bonds form between atoms of the same element.

29) The ionic bond of sodium chloride is formed as a result of:

A) sodium and chlorine sharing electrons.

B) both sodium and chlorine losing electrons.

C) sodium gaining an electron from chlorine.

D) sodium giving up an electron to chlorine.

E) sodium giving up a proton to chlorine.

30) Potassium has one electron in its fourth shell, and chlorine has seven electrons in its third shell. Which of the following is most likely to be true?

A) Chlorine will give an electron to potassium to form an ionic bond.

B) Potassium will give an electron to chlorine to form an ionic bond.

C) The two atoms will share the electron unequally in a polar covalent bond.

D) The two atoms will share an electron equally in a nonpolar covalent bond.