What unique identifier is used to distinguish elements in the periodic table?

• Neutron number

• Electron number

• Proton number

• Atomic mass

What happens to an atom when it becomes an ion?

• It gains or loses electrons

• It gains or loses neutrons

• It gains or loses protons

• It changes its atomic number

Where can electrons be added or removed in an atom?

• From the inner shells

• From the proton shell

• From the nucleus

• From the outermost shell

If ion U has 16 protons and 18 electrons, what is its charge?

• Neutral

• Positive

• Negative

• Cannot be determined

How many extra electrons does ion V have if it has 17 protons and 18 electrons?

• Three

• One

• None

• Two