Chapter 2 Assessment

Which statement is true of all atoms that are anions? a. The atom has more electrons than protons. b. The atom has more protons than electrons. c. The atom has fewer protons than does a neutral atom of the same element. d. The atom has more neutrons than protons.

a. The atom has more electrons than protons.

In the term trace element, the adjective trace means that a. the element is required in very small amounts. b. the element can be used as a label to trace atoms through an organism's metabolism. c. the element is very rare on Earth. d. the element enhances health but is not essential for the organism's long-term survival.

a. the element is required in very small amounts.

Each element has it own characteristic atom in which a. the atomic mass is constant. b. the atomic number is constant. c. the mass number is constant. d. Two of the above are correct.

b. the atomic number is constant.

The reactivity of an atom arises from a. the average distance of the outmost electron shell from the nucleus. b. the existence of unpaired electrons in the valence shell. c. sum of potential energies of all the electron shells. d. the potential energy of the valence shell.

b. the existence of unpaired electrons in the valence shell.

A sodium ion (Na+) contains 10e-, 11p, and 12n. What is the mass number of sodium? a. 11 b. 12 c. 23 d. 33

c. 23

What is the difference between a molecule and a compound? a. There is no difference; the terms are interchangeable. b. A molecule consists of two or more covalently bonded atoms; a compound contains two or more atoms held together by ionic bonds. c. A compound consists of two or more elements in a fix ratio; a molecule has two or more covalently bonded atoms of the same or different elements. d. Compounds always consist of molecules, but molecules are not always compounds.

c. A compound consists of two or more elements in a fix ratio; a molecule has two or more covalently bonded atoms of the same or different elements.

A triple covalent bond would a. not be possible. b. involve the bonding of six atoms. c. produce a triangularly shaped molecule. d. involve the sharing of six electrons.

c. produce a triangularly shaped molecule.

Which of the following statements correctly describes any chemical reaction that has reached equilibrium? a. The concentrations of reactants and products are equal. b. The reactions is now irreversible. c. Both forward and reverse reactions have halted. d. The rates of the forward and reverse reactions are equal.

d. The rates of the forward and reverse reactions are equal.

Which of the following is not a trace element in the human body? a. iodine b. zinc c. iron d. calcium

d. calcium

Compared with 31 P, the radioactive isotope 32P has a. a different atomic number. b. one more proton. c. one more electron. d. one more neutron.

d. one more neutron.

Radioactive isotopes can be used in studies of metabolic pathways because a. their half-life allows a researcher to time an experiment. b. they are more reactive. c. the cell does not recognize the extra protons in the nucleus, so isotopes are readily used in metabolism. d. their location or quantity can be experimentally determined because of their radioactivity.

d. their location or quantity can be experimentally determined because of their radioactivity.