Question

The table below shows the boiling points of some halogens.

Halogen
Boiling point in °C
Bromine
60
Chlorine
−34
Fluorine
−188
Explain the trend in the boiling points of the halogens.

Answer 1

The trend in the boiling points of the halogens is that it increases as you move down the group, due to the increase in molecular size and strength of intermolecular forces. Fluorine has the lowest boiling point of -188°C, chlorine has a higher boiling point of -34°C, and bromine has an even higher boiling point of 60°C.

Step-by-step explanation:

The trend in the boiling points of the halogens is that it increases as you move down the group. Fluorine has the lowest boiling point of -188°C, chlorine has a higher boiling point of -34°C, and bromine has an even higher boiling point of 60°C. This trend can be explained by the increase in molecular size and the strength of the intermolecular forces.

The boiling point of a substance is influenced by its molecular size and the strength of the intermolecular forces. As you move down the halogen group, the atomic radius increases and larger and heavier atoms and molecules exhibit stronger dispersion forces. This results in increased boiling points.

For example, fluorine (F₂) has the lowest boiling point among the halogens because it is the smallest and lightest atom, and its intermolecular forces are weak London dispersion forces. On the other hand, bromine (Br₂) has a higher boiling point because it is larger and heavier, with stronger dispersion forces. The larger molecular size and stronger intermolecular forces make it more difficult for the molecules to break apart and transition from a liquid to a gas, resulting in a higher boiling point.

Answer 2

The boiling point of halogens increases down the family.

Step-by-step explanation:

Boiling Point

Boiling point has multiple factors, but for the purposes of this question, the main factor is IMFs. IMFs are intermolecular forces. IMFs are the attractions that occur between the atoms or molecules of a sample. The stronger the IMFs, the higher the boiling point. This is because strong IMFs hold the molecules together, so it takes more energy to break the attractive forces.

Polarizability

Pure halogens are always non-polar. This means that there are no dipoles or other forms of permanent electron shifts. Since all halogens are nonpolar, there is only one type of IMF: London Dispersion Forces. LDFs are the attractive forces caused by the temporary and random shifts of electron clouds. All molecules experience LDFs. However, LDFs have varying strengths. The larger the molecule, the stronger the LDF. This is due to polarizability. Polarizability is the ease with which electron clouds can shift. Bigger molecules have larger electron clouds, hence the higher polarizability and stronger LDFs.

Since halogens further down the table are larger, both in atomic radius and electron cloud, they have higher polarizability. This leads to stronger LDFs and IMFs. As stated in the first paragraph, strong IMFs cause higher boiling points. This is why larger molecules like Bromine have higher boiling points than small molecules like Fluorine.