Atoms and molecules

Approximately how many elements are there on the periodic table?

• 50

• 100

• 110

• 120

Who first used the word "atom"

• The Greeks

• The Italians

• The Romans

• The Koisan

What is the symbol for helium on the periodic table?

• H

• He

• Hel

• HE

what is the correct description of a molecule?

• Two or more atoms joined by chemical bonds.

• Many atoms linked by chemical bonds

• Two or more different atoms joined by chemical bonds

• Two or more identical atoms linked by chemical bonds

The main difference between an element and a compound is that......

• Elements are small, compounds are big

• Elements have chemical bonds, compounds do not

• Elements are big, compounds are small.

• Elements contain a single type of atom whereas compounds have more than one type of atom.

The difference between a cation and an atom is that....

• a cation has a positive charge and an atom is negative

• a cation has a positive charge and an atom is neutral

• a cation has a negative charge and an atom is neutral

• a cation has a negative charge and an atom is positive.

Which of the following correctly displays the charges on the subatomic particles.

• protons and neutrons are positive while electrons are negative

• protons are neutral, neutrons are positive and electrons are negative

• protons are positive, neutrons are neutral and electrons are negative

• protons are negative, neutrons are neutral and electrons are positive.

what is the mass of a hydrogen atom?

• 1 atomic mass unit

• 2 atomic mass units

• 3 atomic mass units

• 4 atomic mass units

An atom of oxygen contains 8 protons, 8 electrons and 8 neutrons. Its atomic mass will be....

• 8 atomic mass units

• 16 atomic mass units

• 24 atomic mass units

• It is impossible to say from the information provided.

If a neutral atom has 5 protons it must have ........ electrons.

• 5

• 10

• 15

• 20