Question

u2 pretest

1. which accounts for most of the mass of an atom?

a. electrons
b. protons
c. neutrons and protons
d. electrons and neutrons

1. this diagram represents a neutral atom of boron - 11. how many protons and neutrons does boron - 11 have?

a. 11 protons, 11 neutrons
b. 11 protons, 0 neutrons
c. 6 protons, 5 neutrons
d. 5 protons, 6 neutrons

1. in the periodic table, the rows are called

a. periods
b. groups
c. classes
d. families

1. an element located at group 18 and period 4 would best be classified as which type of substance?

a. a halogen c. a metalloid
b. a lanthanoid d. a nonmetal

1. which pair of elements has the most physical and chemical properties in common?

a. ge and se c. k and kr
b. al and ga d. ba and bi

1. this is an electron dot diagram: which element is represented?

a. boron (b)
b. phosphorus (p)
c. sulfur (s)
d. bromine (br)

Explanation:

1. Protons and neutrons are located in the nucleus and have significant mass compared to electrons. Electrons have negligible mass.
2. The atomic number of boron is 5, so it has 5 protons. The mass - number of boron - 11 is 11. Mass number = number of protons+number of neutrons, so number of neutrons = 11 - 5=6.
3. In the periodic table, rows are called periods and columns are called groups or families.
4. Group 18 elements are noble gases, which are non - metals.
5. Elements in the same group have similar physical and chemical properties. Al (aluminum) and Ga (gallium) are in Group 13.
6. The electron - dot diagram shows 5 valence electrons. Phosphorus has 5 valence electrons.

Answer:

1. c. neutrons and protons
2. d. 5 protons, 6 neutrons
3. a. Periods
4. d. a nonmetal
5. b. Al and Ga
6. b. phosphorus (P)