Chemistry Section 3
1.14
- Atom - the building block of matter comprised of three subatomic particles:
protons, neutrons and electrons
- Molecule - group of atoms chemically bonded together
1.15
- Protons and electrons make up the nucleus
- Electrons float around the nucleus in shells
- Max 2 electrons in first shell, then the rest are max 8 (in GCSE)
- Inner shell must be full before next shell fills up
1.16
- Atomic number - proton number
- Mass number - number of protons + number of neutrons
- Relative atomic mass (Ar) - ratio of an atom’s weight compared to hydrogen
(1/12 of carbon) e.g. Ar of O2 is 36 - (2x16)
- Isotope - 2+ forms of the same element with the same number of protons
but a different number of electrons so have different Ar but same chemical
properties
1.17
- Ar = total mass of atoms / total number of atoms
- E.g.
Mass number Abundance
35 75%
37 25%
- (35x75) + (37x25) / (75+25)
1.14
- Atom - the building block of matter comprised of three subatomic particles:
protons, neutrons and electrons
- Molecule - group of atoms chemically bonded together
1.15
- Protons and electrons make up the nucleus
- Electrons float around the nucleus in shells
- Max 2 electrons in first shell, then the rest are max 8 (in GCSE)
- Inner shell must be full before next shell fills up
1.16
- Atomic number - proton number
- Mass number - number of protons + number of neutrons
- Relative atomic mass (Ar) - ratio of an atom’s weight compared to hydrogen
(1/12 of carbon) e.g. Ar of O2 is 36 - (2x16)
- Isotope - 2+ forms of the same element with the same number of protons
but a different number of electrons so have different Ar but same chemical
properties
1.17
- Ar = total mass of atoms / total number of atoms
- E.g.
Mass number Abundance
35 75%
37 25%
- (35x75) + (37x25) / (75+25)
