# THE ELEMENTS

#### branchMATTER & ATOMS

Coming from ATOMIC STRUCTURE
=The Elements= We now know that there are different types of atoms. Each type of atom each has a different number of protons, neutrons and electrons. Substances that consist of only one type of atom are called '''elements'''. There are only about 92 naturally occurring elements. Each element has a name, symbol, atomic number and atomic mass number. [image:http://i.imgur.com/pe1Da9j.png] The Atomic Number = the number of protons The Mass Number = the number of protons & neutrons (the mass of the nucleus) Note that because electrons are so tiny their mass can be ignored. Thus, the mass number represents the mass of the element. The larger the mass number the heavier the element. To work out the number of neutrons we can simply subtract the Atomic number form the mass number. ===The acronym PEA MAN many help you remember this=== ==='''P'''rotons and '''E'''lectrons = '''A'''tomic Number=== ==='''M'''ass number - '''A'''tomic Number = '''N'''eutrons=== ==Examples== Lithium has an atomic number of 3 and a mass number of 7 Therefore Lithium has... 3 Protons 3 Electrons 7-3 = 4 Neutrons We ca now draw a lithium atom: ===[image:http://i.imgur.com/0AKqWMT.png]=== [image:http://i.imgur.com/79OVv1V.png?1]