11) The mass number represents the number of

A) protons in an atom.

B) electrons in an ion.

C) neutrons in an atom.

D) protons and neutrons.

E) neutrons and electrons.

12) Which of the following is sometimes used in diagnostic imaging?

A) a radioisotope

B) a proton

C) an ion

D) an atom

E) an electrolyte

13) How many electrons do most atoms need in their second outer shell in order to be stable?

A) two

B) three

C) four

D) six

E) eight

14) If an element is composed of atoms with an atomic number of 8 and a mass number of 14, then an electrically neutral atom of this element contains

A) 6 protons.

B) 6 neutrons.

C) 6 electrons.

D) 14 protons.

E) 14 electrons.

15) Which is the correct description of a molecule?

A) It is an electrically charged atom.

B) It cannot be broken down physically.

C) It is comprised of two or more elements bonded together.

D) It is the smallest unit of matter.

E) It is comprised of two or more atoms sharing electrons.

16) Combinations of atoms that contain two or more different elements are called

A) molecules.

B) compounds.

C) mixtures.

D) isotopes.

E) None of these are correct.

17) Ions with a negative charge are called

A) cations.

B) anions.

C) radicals.

D) polyatomic ions.

E) None of these are correct.

18) Covalent bonds are formed when

A) atoms share electrons.

B) cations and anions are held together by their opposite charges.

C) electrons are exchanged between atoms.

D) hydrogen forms bonds with negatively charged atoms in the same or different molecules.

E) two or more atoms lose electrons at the same time.

19) When an anion and a cation are electrically attracted to each other, ________ is formed.

A) an ion

B) a molecule

C) a hydrogen bond

D) an ionic bond

E) a covalent bond

20) A molecule containing two atoms of hydrogen and one atom of oxygen in combination is called a(n) ________.

A) oxygen molecule

B) carbon dioxide molecule

C) water molecule

D) hydroxyl molecule

E) hydroxide molecule