- 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
The structure of the Carbon atom
The atom is the smallest part of an element that exists even though it can be divided into smaller particles. The atom is the smallest part as it retains the properties of the element while the subatomic particles do not.
- 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.
- 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
The symbol key for Carbon as represented in the periodic table – C is the symbol for Carbon and 12 is the mass number and 6 is the atomic number
The Periodic Table – Chemist’s best friend!
- You will be provided with a periodic table in your Chemistry exams
- You need to be able to use the names and symbols for the first 20 elements in the table
- You also need to be able to use the name and symbols of the elements in group 1, group 7 and any other elements specified in these notes