Sodium metal: Physical & Chemistry Properties

Physical properties of sodium

Sodium belongs to the alkali metals group and is a solid at normal temperature and pressure. Its melting point is approximately 97.8°C and its boiling point is around 882.9°C. Sodium is a light metal with a density of about 0.97g/cm³, allowing it to float on water. Pure sodium metal has a silvery appearance, but it quickly oxidizes in the air to form sodium oxide on its surface, which makes it appear grayish. Sodium is a soft metal and can be cut with a knife or crushed with fingers. It exhibits good thermal and electrical conductivity and can be used as a heat transfer medium in nuclear power plants when mixed with potassium.

Chemical properties of sodium

It has a total of 11 electrons, and its outermost shell has one electron that is easily taken by other elements. Therefore, sodium can actively react with substances that is h2 oxidative.

Reaction of sodium with oxygen

At room temperature, sodium reacts with oxygen to forming a thin layer of sodium oxide (Na₂O) on its surface gradually. The shiny metallic surface becomes dull and grayish.

4Na(s) + O₂(g) → 2Na₂O(s)

When sodium burns in an abundant supply of oxygen, it produces a bright yellow flame and releases a large amount of heat. The product of this chemical reaction is sodium peroxide (Na₂O₂).

2Na(s) + O₂(g) → Na₂O₂(s)

Reaction of sodium with chlorine

When sodium reacts with chlorine gas, a highly exothermic and explosive reaction occurs. The product is sodium chloride that commonly known as table salt. This is a classic example of a redox reaction. Chlorine is a highly electronegative element, and it readily accepts one electron from sodium atom during the reaction.

2Na(s) + Cl₂(g) → 2NaCl(s)

Reaction of sodium with alcohol

During this reaction, the sodium metal reacts with the alcohol, displacing a hydrogen atom from the alcohol molecule and forming an alkoxide compound. This reaction is not as violent as the reaction between sodium and water. Unlike water, sodium is denser than alcohols with fewer carbon atoms, so it sinks to the bottom and constantly releases hydrogen.

2R-OH(l) + 2Na(s) → 2R-O-Na(aq) + H₂(g)

R represents an organic group or alkyl group attached to the oxygen atom of the alcohol.

Reaction of sodium with water

In a beaker filled with water and phenolphthalein, and a small piece of sodium is introduced. Due to sodium's lower density than water, it floats on the surface. Sodium reacts vigorously with water to release a significant amount of heat, and it melts into a small liquid sphere. As this chemical reaction generates hydrogen gas, the liquid sphere moves erratically on the water's surface, and its size gradually diminishes until it completely disappears. The phenolphthalein solution becomes pink due to sodium hydroxide.

2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)

Since sodium is highly reactive with both water and oxygen, in the laboratory, it is immersed in a glass bottle containing kerosene to isolate it from air and water.

Frequently Asked Questions