Periodicity Reference Sheet printable pdf download

PERIODICITY

Classification of elements in s, p, d blocks

Elements are classified as s, p or d block, according

to which orbitals the highest energy electrons are in.

Period 2 = Li, Be, B, C, N, O, F, Ne

Period 3 = Na, Mg, Al, Si, P, S, Cl, Ar

0.18

Atomic radius

0.16

Atomic radii decrease as you move from left to right

0.14

across a period, because the increased number of

0.12

protons create more positive charge attraction for

0.1

electrons which are in the same shell with similar

0.08

0.06

shielding.

0.04

0.02

Exactly the same trend in period 2

1st ionisation energy

There is a general trend across is to increase. This is due to

1600

increasing number of protons as the electrons are being

1400

added to the same shell

1200

1000

800

There is a small drop between Mg + Al. Mg has its outer

600

electrons in the 3s sub shell, whereas Al is starting to fill the

400

3p subshell. Al’s electron is slightly easier to remove

200

because the 3p electrons are higher in energy.

There is a small drop between phosphorous and sulphur.

Sulphur’s outer electron is being paired up with an another

Exactly the same trend in period 2 with

electron in the same 3p orbital.

drops between Be & B and N to O for

When the second electron is added to an orbital there is a

same reasons- make sure change 3s

slight repulsion between the two negatively charged

and 3p to 2s and 2p in explanation!

electrons which makes the second electron easier to remove.

Melting and boiling points

3000

For Na, Mg, Al- Metallic bonding : strong bonding – gets

stronger the more electrons there are in the outer shell that

2500

are released to the sea of electrons. A smaller positive centre

2000

also makes the bonding stronger. Higher energy is needed to

1500

break bonds.

1000

Si is Macromolecular: many strong covalent bonds between

500

atoms, high energy needed to break covalent bonds– very

high mp +bp

Na Mg

, S

, P

- simple Molecular : weak van der waals

2 (g)

8 (s)

4 (S)

between molecules, so little energy is needed to break them –

Similar trend in period 2

low mp+ bp

Li,Be metallic bonding (high mp)

B,C macromolecular (very high mp)

has a higher mp than P

because it has more electrons

molecular (gases! Low mp as

=128)(P

=60) so has stronger v der w between molecules

small v der w)

Ar is monoatomic weak van der waals between atoms

Ne monoatomic gas (very low mp)

N Goalby

Periodicity Reference Sheet

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