Anh KT

The atomic number of an element is determined by

• the number of neutrons.

• the number of protons.

• the number of neutrons plus the number of protons.

• the number of electrons.

The atomic weight of an element is approximately determined by

• the number of neutrons.

• the number of protons.

• the number of neutrons plus the number of protons.

• the number of electrons.

Suppose there is an atom of oxygen, containing eight protons and eight neutrons in the nucleus, and two neutrons are added to the nucleus. What is the resulting atomic weight?

• 8

• 10

• 16

• 18

An ion

• is electrically neutral.

• has positive electric charge.

• has negative electric charge.

• can have either a positive or negative charge.

An isotope

• is electrically neutral.

• has positive electric charge.

• has negative electric charge.

• can have either a positive or negative charge.

A molecule

• can consist of a single atom of an element.

• always contains two or more elements.

• always has two or more atoms.

• is always electrically charged.

In a compound,

• there can be a single atom of an element.

• there must always be two or more elements.

• the atoms are mixed in with each other but not joined.

• there is always a shortage of electrons.

An electrical insulator can be made a conductor

• by heating it.

• by cooling it.

• by ionizing it.

• by oxidizing it.

Of the following substances, the worst conductor is

• air.

• copper.

• iron.

• salt water.

Of the following substances, the best conductor is

• air.

• copper.

• iron.

• salt water.