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THE PERIODIC TABLE
occur in the same vertical columns (GROUPS).
= the elements arranged in rows (PERIODS)
such that chemically similar elements
in order of increasing atomic number (Z)
Period 1
Period 2
Period 3
Period 4
Period 5
Period 6
Period 7
Gro
up
1
Gro
up
2
Gro
up
3
Gro
up
4G
rou
p 5
Gro
up
6G
rou
p 7
Gro
up
0
Group VII
GROUP
Group number = number of electrons in highest occupied energy level
e.g. Group I the alkali metals
the halogens
eg Na[2,8,1] =
eg F[2,7] =
= elements within the same vertical column
Chemical and physical properties are similar within a group
even though more p+ are present.
This causes a WEAKER attractive force and consequently, a lowering of ionisation energy
DECREASES because the outer e- is more distant and more shielded from attracting nuclear protons,
M (g) M+(g) + e-
even though more p+ are present.
This causes a WEAKER attractive force and consequently, a lowering of ionisation energy
DECREASES because the outer e- is more distant and more shielded from attracting nuclear protons,
M (g) M+(g) + e-
even though more p+ are present.
This causes a WEAKER attractive force and consequently, a lowering of ionisation energy
DECREASES because the outer e- is more distant and more shielded from attracting nuclear protons,
M (g) M+(g) + e-
attractions between 2+ cations and the 2 delocalised electrons per atom become WEAKER.
DECREASE A s metallic bonding gets WEAKER because radius and mass of the 2+ ions INCREASE
Mg unusual because atoms DO NOT pack together as well as others
attractions between 2+ cations and the 2 delocalised electrons per atom become WEAKER.
DECREASE A s metallic bonding gets WEAKER because radius and mass of the 2+ ions INCREASE
Mg unusual because atoms DO NOT pack together as well as others
attractions between 2+ cations and the 2 delocalised electrons per atom become WEAKER.
DECREASE A s metallic bonding gets WEAKER because radius and sheilding of the 2+ ions INCREASE
Mg unusual because atoms DO NOT pack together as well as others
PERIOD
Chemical and physical properties change from extremes across any period.
e.g. Period 3
Sodium = a reactive metallic solid
Argon = an unreactive, non- metallic gas
eg Si (Z=14)
Period number = number of shells
2,8,4 Period 3 and Group 4
= elements within the same horizontal row
Atomic Radii Across Period 3
0
0.05
0.1
0.15
0.2
0.25
10 11 12 13 14 15 16 17 18
Atomic Number (Z)
Ato
mic
Radiu
s / n
m
Outer e- in same energy level (distance & shielding similar)
but attracted more strongly as no. of nuclear protons increases
Atomic radius DECREASES across period 3.
MELTING POINTMELTING POINT
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
PeriodsA general increase then a decrease
Kelvin SODIUM MAGNESIUM
MELTING POINTMELTING POINT
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
PeriodsA general increase then a decrease
Metals Na-AlMelting point increases due to the increasing strength of metallic bonding caused by ...
the larger number of electrons contributing to the “cloud”
larger charge and smaller size of ions gives rise to a larger charge density.
Kelvin
The electron cloud in magnesium is denser than in sodium so more energy is required to separate the ‘ions’
SODIUM MAGNESIUM
MELTING POINTMELTING POINT
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
PeriodsA general increase then a decrease
Metals Na-AlMelting point increases due to the increasing strength of metallic bonding caused by ...
the larger number of electrons contributing to the “cloud”
larger charge and smaller size of ions gives rise to a larger charge density.
Kelvin
The electron cloud in magnesium is denser than in sodium so more energy is required to separate the ‘ions’
SODIUM MAGNESIUM
MELTING POINTMELTING POINT
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
Non-metals Si-Ar
SILICON Large increase in melting point as it has a giant molecular structure like diamond
A lot of energy is required to break the many covalent bonds holding the atoms together.
Kelvin
MELTING POINTMELTING POINT
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
P, S, Cl, ArVery much lower melting points as they are simple covalent molecules
Melting point depends on the weak intermolecular van der Waals’ forces.
The larger the molecule the greaterthe van der Waals’ forces
P4 S8 Cl2
relative mass 124 256 71
melting point 44°C 119°C -101°C
Kelvin
MELTING POINTMELTING POINT
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
PHOSPHORUS
can exist is several allotropic forms. In the most common, red phosphorus, each molecule exists in a tetrahedral structure. The atoms are joined by covalent bonds within the molecule
formula P4
relative mass 124melting point 44°C
Melting point drops dramatically as intermolecular attractions are now due to weak van der Waals’ forces.
Kelvin
MELTING POINTMELTING POINT
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
SULPHUR
can exist is several allotropic forms. Sulphur usually exists in a puckered eight membered ring structure. The atoms are joined by covalent bonds within the molecule
formula S8
relative mass 256melting point 119°C
Melting point rises slightly as the molecule is bigger so has slightly stronger van der Waals’ forces.
Kelvin
MELTING POINTMELTING POINT
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
CHLORINE
Exists as a linear diatomic molecule.
The atoms are joined by covalent bonds within the molecule
formula Cl2
relative mass 71melting point -101°C
Melting point falls slightly as the molecule is smaller so has slightly lower van der Waals’ forces.
Kelvin
MELTING POINTMELTING POINT
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
ARGON
Exists as a monatomic species.
formula Arrelative mass 40melting point -189 °C
Melting point falls.
Kelvin
MELTING POINT TREND - NON METALSMELTING POINT TREND - NON METALS
P4 S8 Cl2 Ar
relative mass 124 256 71 40melting point / K 317 392 172 84
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Boiling points tend to be a better measure and show better trends because solids can be affected by the crystal structure as well as the type of bonding.
As is expected, the boiling points are higher than the melting points.
Kelvin
BOILING POINTBOILING POINT
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Boiling points tend to be a better measure and show better trends because solids can be affected by the crystal structure as well as the type of bonding.
As is expected, the boiling points are higher than the melting points.
Kelvin
BOILING POINTBOILING POINT
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.
Na Mg Al Si P S Cl Ar
3000
2500
2000
1500
1000
500
0
Note the trend from Al – Si varies slightly when we consider the mpt trend and the bpt trend. The mpt increases from Al – Si but the bpt decreases.
The is because when Silicon melts many of its covalent bonds are broken so to vaporize molten silicon does not require as much energy as to vaporize molten Aluminium
Kelvin
BOILING POINTBOILING POINT
Boiling and melting points are a measure of the energy required toseparate the particles in a substance. Bond type is significant.