Atomic Structure and the Periodic table - Definitions

Question 1

Atomic Number

Answer 1

The atomic number of an atom is the number of protons in its nucleus. (The term proton number is sometimes used for atomic number)

Question 2

Mass Number

Answer 2

The mass number of an atom is the number of protons plus neutrons in its nucleus.

Question 3

Molar Mass

Answer 3

Molar mass is the mass of one mole of a chemical - the unit is gmols−1

Question 4

Molecular formula

Answer 4

A molecular formula shows the number of atoms of the different element in one molecule of a compound. (eg, CH3 for methane)

Question 5

ratio

Empirical Formula

Answer 5

An Empirical formula shows the simplest whole number ratio of the atoms of different elements in a compound

Question 6

elements

Isotope

Answer 6

Isotopes are atoms of the same element with the same atomic number but different mass number

Question 7

carbon-12

Relative isotopic mass

Answer 7

relative isotopic mass is the mass of one atom of carbon-12, for which the relative mass is defined as exactly 12

Question 8

carbon -12

Relative atomic mass

Answer 8

This is the weighted average mass of an atom of an element relative to the mass of one atom of carbon-12, for which the relative mass is defined as exactly 12.

Question 9

energy

First ionisation energy

Answer 9

The first ionisation energy of an element is the energy needed to remove one electron from each atom in one mole of gaseous atoms.

Question 10

Energy amounts

Successive ionisation Energies

Answer 10

These are the energy amounts needed to remove successive electrons of an element one by one from each atom (according to the number of electrons in the atom), in one mole of gaseous atoms/ions