What are isotopes?

When are two atoms the same?

• When the mass number is the same.

• When the electron number is the same.

• When the atomic mass/proton number is the same.

• When the neutron mass/proton number is the same.

What best defines isotopes?

• When two atoms have the same mass number but different number of electrons.

• When two atoms have the same number of protons but different number of neutrons.

• When two atoms have the same number of neutrons but a different number of protons.

• When all the numbers are the different.

Protium is a name for the most commonly occurring atom of Hydrogen. How many neutrons does protium have?

• 0

• 1

• 2

• 3

How is tritium, a 'heavy hydrogen' isotope different to protium?

• Same number of electrons, same number of protons, same number of neutrons.

• One extra neutron, same number of protons, same number of electrons.

• One extra proton, same number of neutrons, same number of electrons.

• Same number of protons, same number of electrons, two extra neutrons.

An isotope of chlorine has a relative mass of 35 and an atomic number of 17. If 35 is the mass of chlorine, how many electrons does a neutral chlorine atom have?

• 17

• 18

• 35

• 37

For every million parts of water, there are approximately 150 deutirium atoms. Deutirium is a heavier isotope of hydrogen. How would a mole of deutirium based water compare to a mole of hydrogen based water?

• A mole of deutirium water and hydrogen water would be identical in terms of number of molecules and mass.

• A mole of deutirium water would have fewer molecules, because each one is heavier than a hydrogen molecule.

• Both would have the same number of molecules, but a mole of deutirium water would be heavier than a mole of hydrogen water.

Electrons are found in atoms...

• In the nucleus

• In shells/orbitals around the nucleus.

• There are no electrons in atoms.

Protons are found in atoms...

• In the nucleus

• In shells/orbitals around the nucleus.

• There are no protons in atoms.

Neutrons are found in atoms...

• In the nucleus

• In shells/orbitals around the nucleus.

• There are no neutrons in atoms.

Which option best describes the relative properties of an electron?

• Charge of -1, negligible (nearly 0) mass.

• Charge of 0, mass of 1

• Charge of +1, mass of 1

• Charge of -1, mass of -1