Atoms

Question 0

Mass number (A)

Answer 0

The sum of protons and neutrons in the nucleus of an atom.

Question 1

Atomic number (Z)

Answer 1

The number of protons in the nucleus of an atom of that element.

Question 2

Protons, Electrons, Neutrons

Answer 2

Proton: +1, 1
Electron: -1, 1/1836
Neutron: 0, 1

Question 3

Isotopes

Answer 3

Atoms of the same element with different numbers of neutrons.

Question 4

Ion

Answer 4

A positively or negatively charged atom or (covalently bonded) group of atoms (a molecular ion).

Question 5

Relative isotopic mass

Answer 5

The mass of an atom of an isotope compared with 1/12th of the mass of an atom of C-12.

Question 6

Relative atomic mass, Ar

Answer 6

The weighted mean mass of an atom of an element compared with 1/12th of the mass of an atom of C-12.

Question 7

Relative molecular mass, Mr

Answer 7

The weighted mean mass of a molecule compared with 1/12th of the mass of an atom of C-12.

Question 8

Relative formula mass

Answer 8

The weighted mean mass of a formula unit compared with 1/12th of the mass of an atom of C-12.

Question 9

Avogadro constant, Na

Answer 9

The number of atoms per mole of the C-12 isotope (6.022*10^23 mol^-1).

Question 10

Mole

Answer 10

The amount of any substance containing as many particles as there are C atoms in exactly 12g of the C-12 isotope.

Question 11

Molar mass, M

Answer 11

The mass per mole of a substance.

Units: gmol^-1

Question 12

Empirical formula

Answer 12

Simplest whole number ratio of atoms of each element present in a compound.

Question 13

Molecule

Answer 13

Small group of atoms held together by covalent bond.

Question 14

Molecular formula

Answer 14

The actual number of atoms of each element in a molecule.

Question 15

Molar volume

Answer 15

The volume per mole of a gas.
Units: dm^-3mol^-1
At rtp, the molar volume is ~24.0.

Question 16

Concentration

Answer 16

Of a solution is the amount of solute, in mol, dissolved per 1dm^-3 of solution.