Unit 1 - fundamentals of science
17/09
Chemistry
● Protons, +1 relative mass 1
● electron, -1 relative mass 1/1840
● Neutron, 0 relative mass 1
In each element, there is the
● Mass number - no. of protons and neutrons
● Atomic number - no. of protons which is equal to
the amount of electrons.
element protons neutrons electrons Mass no. Atomic no.
hydrogen 1 0 1 1 1
aluminium 13 14 13 27 13
titanium 22 26 22 48 22
krypton 36 48 36 84 36
Oxygen -16 8 8 8 16 8
Oxygen -18 8 10 8 18 8
Levels and sub-levels
The Aufbau principle states that the lowest energy sub-levels are occupied first.
There are four sublevels labelled in order of increasing energy, each holds a different number of
electrons.
● S
● P
● D
● F
, Unit 1 - fundamentals of science
This is in order of lowest to highest and represents the different levels and sublevels.
sublevel Max no of electrons it can hold
S 2
P 6
D 10
F 14
17/09
Chemistry
● Protons, +1 relative mass 1
● electron, -1 relative mass 1/1840
● Neutron, 0 relative mass 1
In each element, there is the
● Mass number - no. of protons and neutrons
● Atomic number - no. of protons which is equal to
the amount of electrons.
element protons neutrons electrons Mass no. Atomic no.
hydrogen 1 0 1 1 1
aluminium 13 14 13 27 13
titanium 22 26 22 48 22
krypton 36 48 36 84 36
Oxygen -16 8 8 8 16 8
Oxygen -18 8 10 8 18 8
Levels and sub-levels
The Aufbau principle states that the lowest energy sub-levels are occupied first.
There are four sublevels labelled in order of increasing energy, each holds a different number of
electrons.
● S
● P
● D
● F
, Unit 1 - fundamentals of science
This is in order of lowest to highest and represents the different levels and sublevels.
sublevel Max no of electrons it can hold
S 2
P 6
D 10
F 14
