Chemistry- beginning(elements)

Elements
An element is a pure substance that cannot be broken down further into simpler substances. 


Chemical symbols are used to represent elements. Each element has a unique symbol consisting of 1 or 2 letters. E.g. the symbol for oxygen is O and the symbol for iron is FE.


Elements can be classified into 2 groups- metals and non-metals.
- some elements have properties of both metals and non-metals. They are called metalloids.
e.g. silicon, germanium, boron and arsenic.

Elements are made up of tiny particles called atoms. The atoms of one element are not the same as the atoms of another element.
Atoms are the smallest particles of an element that have the chemical properties of that element.

-> Gold ring is made of the element gold which consists of
gold atoms (Solid)
 -> The neon element  as gas is used in advertising 

signs and consists entirely of neon atoms. (Gas)

Elements that exist as individual atoms -> monatomic elements

(atoms are not joined together chemically)


A molecule is a group of two or more atoms that are chemically combined.
e.g. A hydrogen molecule is made up of 2 hydrogen atoms chemically combined.
An ozone is formed when 3 atoms of oxygen are chemically combined. (ozone has the molecular formula O3.
e.g of water molecule:

Molecules formed by the combination of 2 atoms are called diatomic molecules.
3 atoms-> triatomic molecules
4 or more atoms-> polyatomic molecules.