Sodium Properties - Chemical and Physical Properties of Sodium

Sodium is a member of alkali metal group and is placed in the periodic table below lithium and above potassium. Chemically, sodium is represented by the symbol Na. Atomic number of sodium is 11 and its atomic mass is 22.98 or 23. As the atomic number of sodium suggests, it has only one electron in its outermost orbit or its valency is +1. Due to this, sodium is a highly reactive chemical element and sodium is found only in the form of compounds. With change in the surrounding physical condition, properties of sodium changes. We have discussed in detail about the chemical and physical properties of sodium in two different sections of this article.

Chemical Properties of Sodium

Sodium chemical properties are all those properties of sodium that are visible only when any reaction is taking place between sodium and any other chemical substance. As per the periodic table, sodium is more reactive as compared to lithium and has less reactive properties than potassium.

Reaction with Oxygen
Sodium readily reacts with oxygen to form sodium oxide. When a fresh piece of sodium comes in contact with air, it forms sodium oxide instantly and this oxide forms a white coating and protects the underlying metal from any further reaction. When sodium is burned in air, it reacts with atmospheric oxygen to form sodium peroxide (Na₂O₂). Whereas on burning in limited supply of oxygen, it forms sodium oxide. If this burning process is carried out under pressure, sodium superoxide (NaO₂) is formed.

Reaction with water
Reaction of sodium with water results in the formation of sodium hydroxide and hydrogen gas. As heat is produced during this reaction, it is called exothermic reaction. This released heat often ignites the hydrogen gas and as a result fire may break out. If large pieces of sodium is put into water it can lead to loud explosions.

Reaction with Ammonia
Under two different conditions, reaction of sodium with ammonia yields two different products. When the reaction takes place in the presence of hot coke or pure carbon, then sodium cyanide (NaCN) and hydrogen gas is obtained. On reaction with liquid ammonia, where iron, cobalt or nickel acts as a catalyst, sodium amide (NaNH₂) and hydrogen gas is formed.

Reaction with Unsaturated Hydrocarbons
Sodium reacts with hydrocarbon compounds with double bonds to make them saturated (single bonded). This type of reaction is often referred to as addition reaction. In this manner, a type of synthetic rubber is formed which is called buna. It has derived its name from butadiene (a type of hydrocarbon) and sodium (Na).

Reaction with Alcohol
On addition of sodium into alcohol, a compound is formed, which is called alkoxide. This reaction has some similarity with its reaction with water as in both the cases sodium replaces one hydrogen atom.

Physical Properties of Sodium

Sodium physical properties are those aspects of the element that can be perceived or measured. These include density, melting point, boiling point, electric conductivity, etc. At room temperature, sodium is found in the form of a solid metallic substance which is very soft to touch. Due to its softness, you can easily cut it even with the help of a table knife. Basically, sodium not exposed to air is silvery-white in color and is bright and shiny. When it is kept in open air, it becomes dull and gray because of the reaction with the oxygen present in the atmosphere. Sodium has an extremely low density and it is a bit lower than that of water. For this reason, if you place it into water, it will float around. Though after some time, it will react violently contact with water and release large amount of heat that may result in outbreak of flame. Both the melting and boiling point of sodium are quite high. Its boiling point is at 883°C and melting point is at 97.72° C. Sodium is a good conductor of electricity, which means that electric current can pass through this element without much resistance.

All these chemical and physical properties of sodium are responsible for the formation of such a large variety of sodium compounds in nature. Some of the sodium reactions are binary (formed by two elements), some are ternary (formed by three elements) and others have more complex forms.