1. 1.2 Monatomic Elements Very Weak Attractions
LO: I know about the weak forces of attraction between atoms of the noble gases.

2. The noble gases are elements as they exist as single atoms at room temperature.
monatomic
If a gas like neon is cooled to a low enough temperature it turns into a
liquid
Cooling
gas
liquid Ne Ne

3. Further cooling turns neon into a .
solid
Further cooling turns neon into a
Cooling Ne
liquid
solid Ne
There must be forces of attraction holding the atoms together.
They are called forces.
van der Waals
Van der Waals forces are very since very little energy is needed to break them in neon.
weak

4. Van der Waals Forces
LO: I understand how van der Waals forces come about.

5. electrostatic
The van der Waals force is the attraction between a momentary slight charge on one atom and the momentary slight opposite charge it causes in a neighbouring atom.
Van der Waals forces are due to uneven charge in a
atom.
neutral
The uneven charge is produced when the electron cloud surrounding the nucleus about creating a temporary slightly negative side to the atom and a temporary slightly positive side.
wobbles
(-)
(+)

6. The dipole on one atom forces a dipole on a atom to form:
This kind of charge separation is called a
dipole
The dipole on one atom forces a dipole on a atom to form:
neighbouring — + — +
van der Waals force
Thus, the two atoms are attracted to each other.

7. The Noble Gas Series
LO: I understand how van der Waals forces affect the boiling points of the noble gases.

8. Boiling point trend down the noble gases group:
(˚C)
Period Number He Ne Ar Kr Xe Ra
increases
The boiling point down a group.
increasing
This is because the atoms are in size.
greater
The larger an atom is the the van der Waals forces present.
energy
More is needed to separate the atoms and so the boiling point is higher.