Peridiocity Of Period 3 Chart printable pdf download

2. PERIODICITY of Period 3

AS Recap

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

0.2

Atomic radius

Atomic radii decrease as you move from left to right

0.15

across a period, because the increased number of

protons create more positive charge attraction for

0.1

electrons which are in the same shell and

therefore have similar shielding.

0.05

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

1200

added to the same shell

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

2500

stronger the more electrons there are in the outer shell that

2000

are released to the sea of electrons. A smaller positive

centre also makes the bonding stronger. High energy is

1500

needed to break bonds.

1000

Si is Macromolecular: many strong covalent bonds

500

between 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)

Similar trend in period 2

between molecules, so little energy is needed to break them

Li,Be metallic bonding (high mp)

– low mp+ bp

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

small v der w)

Ne monoatomic gas (very low mp)

Ar is monoatomic weak van der waals between atoms

N Goalby

Peridiocity Of Period 3 Chart

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