2. Explaining the trend in melting points
The melting points of the
elements decrease down
group 1.
3. Explaining the trend in melting points
The melting points of the Melting
elements decrease down Element
point (K)
group 1.
Lithium 454
A metal’s melting point depends
on the strength of its metallic Sodium 371
bonds. This decreases down the
Potassium 336
group because the atomic radius
increases, resulting in a weaker Rubidium 312
attraction between the nucleus
Caesium 302
and delocalized electrons.
4. Explaining the trend in melting points
The melting points of the Melting
elements decrease down Element
point (K)
group 1.
Lithium 454
A metal’s melting point depends
on the strength of its metallic Sodium 371
bonds. This decreases down the
Potassium 336
group because the atomic radius
increases, resulting in a weaker Rubidium 312
attraction between the nucleus
Caesium 302
and delocalized electrons.
large radius
weak attraction
Small radius
Strong attraction
5. Trend in Mp of halogens?
The halogens are the elements in Group 7 of the
periodic table.
6. Trend in Mp of halogens?
The halogens are the elements in Group 7 of the
periodic table.
7. Trend in Mp of halogens?
The halogens are the elements in Group 7 of the
periodic table.
The name halogen comes from the Greek
words for salt-making.
8. Trends in boiling point
Halogen molecules increase in size down the group. This
leads to greater van der Waals forces between molecules,
increasing the energy needed to separate the molecules
and therefore higher melting and boiling points.
9. Trends in boiling point
Halogen molecules increase in size down the group. This
leads to greater van der Waals forces between molecules,
increasing the energy needed to separate the molecules
and therefore higher melting and boiling points.
fluorine
atomic radius = 42 × 10-12 m
boiling point = -118 °C
10. Trends in boiling point
Halogen molecules increase in size down the group. This
leads to greater van der Waals forces between molecules,
increasing the energy needed to separate the molecules
and therefore higher melting and boiling points.
fluorine iodine
atomic radius = 42 × 10-12 m atomic radius = 115 × 10-12 m
boiling point = -118 °C boiling point = 184 °C
11. Trends in boiling point
Halogen molecules increase in size down the group. This
leads to greater van der Waals forces between molecules,
increasing the energy needed to separate the molecules
and therefore higher melting and boiling points.
van der
Waals forces
fluorine iodine
atomic radius = 42 × 10-12 m atomic radius = 115 × 10-12 m
boiling point = -118 °C boiling point = 184 °C
