Concise Selina Solutions for Class 6 Chemistry Chapter 4 Elements, Compounds, Symbols and Formulae


Elements:

A pure substance which is made up of only one kind of atom and cannot be broken into two or simpler substances by physical or chemical means is referred to as an element. Example: Zinc, Sulphur.

Compounds:

They are made up of one or more elements and are denoted by chemical formulae. A compound contains atoms of different elements chemically combined in a fixed ratio. The smallest unit of a compound is a molecule Compounds contain different elements in a fixed ratio arranged in a defined manner through chemical bonds. A compound can be broken down into simpler substances by chemical methods/reactions. A compound is represented using a formula-example: Water (H2O), Sodium chloride (NaCl), Magnesium oxide (MgO).

Symbols to represent elements:

A symbol represents each element. It is usually derived from the first letter of its name in English or Latin. The first letter of the symbol is always in upper case. The starting alphabet of its name represents some elements. Example: Carbon is represented as C. Symbols of some elements are the first two alphabets, where the second alphabet is in the lower case. Example: Sodium is represented as Na, where Natrium is the Latin name of sodium.

Formulae

A chemical formula is used as a quick way to show the composition of compounds. Letters, numbers, and symbols are used to represent elements and the number of elements in each compound.