Sodium is a chemical element with the symbol Na and atomic number 11. It belongs to Group 1 of the periodic table, known as the alkali metals. Sodium has 11 protons in its nucleus and 11 electrons arranged in three electron shells. The electron configuration is 1s² 2s² 2p⁶ 3s¹, with one valence electron in the outermost shell.
Sodium has several distinctive physical properties. It is a soft, silvery-white metal that can be cut with a knife. It has a relatively low melting point of 98 degrees Celsius and a low density of 0.97 grams per cubic centimeter, making it less dense than water. Sodium is also an excellent conductor of both heat and electricity, which is typical of metals.
Sodium is extremely reactive due to its single valence electron. It readily loses this electron to form a positively charged sodium ion, Na plus. This reaction can be represented as sodium atom giving up an electron to become sodium ion plus a free electron. Sodium reacts so vigorously with water that it must be stored under oil to prevent contact with moisture in the air.
Due to its high reactivity, sodium is never found free in nature. It always exists in chemical compounds. The most common sodium compound is sodium chloride, or table salt, which forms a crystal lattice structure. Sodium compounds are abundant in seawater, and other important compounds include sodium carbonate and sodium hydroxide, which have various industrial applications.
In summary, sodium is a highly reactive alkali metal with atomic number 11. It is characterized by its soft, silvery-white appearance, low density, and low melting point. Due to its single valence electron, sodium readily forms positive ions and is never found free in nature. Its compounds are essential in many applications, from table salt in our food to soap production and even sodium vapor in street lighting.