Atoms consist of a central containing protons and . The nucleus is surrounded by arranged in energy levels (also called shells). Atoms have no electric charge because they contain the same number of and electrons.

are neutral, so have a charge of 0.

Atoms and ions of the same element always have the same number of .

The mass number tells you the number of and neutrons in the of the atom.

number = number of protons

Using the nuclear symbol given above, fill in the following missing values:

Atomic number:

Number of protons:

Using the nuclear symbol given above, fill in the following missing values:

Mass number:

Number of neutrons:

The above nuclear symbol represents uranium-235, fill in the missing values:

Atomic number:

Mass number:

Number of protons:

Number of neutrons:

Number of electrons:

The above nuclear symbol represents uranium-238, fill in the missing values:

Mass number:

Number of neutrons:

Using the data in the table above, work out the missing values.

Atom or ion:

Number of electrons:

Using the data in the table above, work out the missing values.

Atom or ion:

Number of electrons:

Using the data in the table above, work out the missing values.

Number of electrons: