a.) wavelength

b.) frequency

c.) velocity

d.) speed

2.which of the following elements is a liquid at room temperature

a.) Hg

b.) H

c.) Na

d.) Ne

3. pure substance may be either element or -

a.) mixtures

b.) solutions

c.) compounds

d.) heterogeneous materials

4. when an atom gains electrons , an ion with a _____ charge is formed

a.) neutral

b.) positive

c.) negative