Physical properties of the alkali metals
The first vertical column of elements in the periodic table, starting with lithium and ending with francium. Also called the alkali metals. contains A substance made of one type of atom only. placed in a vertical column on the far left of the A tabular representation of all known elements in order based on atomic number, eg all the noble gases are found on the right of the periodic table.. The elements in group 1 are called the The first vertical column of elements in the periodic table, starting with lithium and ending with francium. Also called group 1..
The alkali metals share similar A description of the appearance of a substance or how it acts without involving chemical reactions. For example, state, melting point, conductivity, etc. and A description of how a substance reacts with other substances. For example, flammability, pH, reaction with acid, etc..
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Physical properties
The alkali metals:
- are soft (they can be cut with a knife)
- have relatively low The temperature at which a solid changes into a liquid as it is heated.
The alkali metals also have low A measure of compactness and the ratio of mass to volume. It is usually measured in kilograms per metre cubed (kg/m3) or grams per centimetre cubed (g/cm3).. They are low enough for the first three (lithium, sodium and potassium) to float on water.
Example
The table shows the melting points of five alkali metals. Use this information to describe how the melting point changes in group 1.
| Element | Melting point |
| Lithium, Li | 180°C |
| Sodium, Na | 98°C |
| Potassium, K | 63°C |
| Rubidium, Rb | 39°C |
| Caesium, Cs | 28°C |
| Element | Lithium, Li |
|---|---|
| Melting point | 180°C |
| Element | Sodium, Na |
|---|---|
| Melting point | 98°C |
| Element | Potassium, K |
|---|---|
| Melting point | 63°C |
| Element | Rubidium, Rb |
|---|---|
| Melting point | 39°C |
| Element | Caesium, Cs |
|---|---|
| Melting point | 28°C |
Going down group 1, the melting point decreases.
Question
Use the information in the table and the chart to predict the melting point of francium, Fr. Explain your answer.
The melting point of francium will be around 23-27°C. This is because francium is below caesium in the periodic table, so it should have a lower melting point, and the difference in melting point decreases going from one element to the next.
