STD IX – LANGUAGE OF CHEMISTRY – ARCHIMEDES

INTRODUCTION TO IMPORTANT TERMS

SYMBOL, VALENCY, FORMULAE OF RADICALS

Chemical Symbols and Valency

Chemistry has its own language such as symbol, equation, ion, valency, atom, element, molecule, reaction and so on. A chemical symbol denotes in short, a particular element or an atom of that element. Chemical reactions are easy to write with chemical symbols than having to write the lengthy chemical names. Many scientists have devised several methods to symbolic representation.

Valency

Valency indicates the combining capacity of an atom or radical. It is defined as the number of hydrogen atoms that will combine with or displace one atom of that element or radical.

Radicals

An atom or a group of atoms that behave like a single unit and contain a positive or negative ion is called a radical. Radicals are very reactive and have a unique valency.

BALANCING

A chemical reaction involves the transformation of one set of chemical substances to another set. It leads to change in the chemical and physical properties of a substance. It also leads to the change in physical state and composition of that substance. Substances with more than two elements chemically bonded are known as compounds. Chemical Formula represents the elements that a compound is made of.

Balancing chemical equations Hit and trial method | Partial equation method

RELATIVE ATOMIC MASS

Molecular Formulae and Equations

A molecular formula, also known as a chemical formula, is a combination of elemental symbols and subscript numbers which is used to show the composition of a compound. Examples: Silica is represented as SiO2 . Marble is represented as CaCO3 .