Chemistry elements

Atoms: The building blocks of matter

All substances are made of tiny particles of matter called atoms which are the building blocks of all matter

Each atom is made of subatomic particles called protons, neutrons, and electrons

The protons and neutrons are located at the centre of the atom, which is called the nucleus

The electrons move very fast around the nucleus in orbital paths called shells

The mass of the electron is negligible, hence the mass of an atom is contained within the nucleus where the protons and neutrons are located

Chemical symbols

An element is a substance made of atoms that all contain the same number of protons and cannot be split into anything simpler.

So, if you had 500g of pure carbon and divided it into 500 x 1g piles, each pile would contain the same substance and would not differ from any other pile.

There is a limited number of elements, and all elements are found on the Periodic Table e.g., hydrogen, carbon, nitrogen.

The most recent Periodic Tables commonly contain around 103 elements although some go up to 118 elements

Each element is represented by its own unique symbol as seen on the Periodic Table e.g., N stands for nitrogen and for nitrogen only.

Where a symbol contains two letters, the first one is always written in uppercase letters and the other in lowercase e.g., sodium is Na, not NA.

The following elements must be written as molecules as they exist in nature as two atoms joined together: H2, N2, O2, F2, Cl2, Br2 and I2.

The atomic number and mass number also shown on the periodic table