A substance that is made of only one sort of atom is called an element Elements O C C C O O O C C C O O C C C O O Eg, Carbon is made up of only carbon atoms Eg, Oxygen is made up of only oxygen atoms A substance that is made of only one sort of atom is called an element

The Periodic table There are about 100 different elements which are shown on the periodic table Metals appear on the left and middle part of the table. Non metals appear on the right hand side of the table The groups contain elements with similar properties

Atoms Particle Mass Charge Proton Neutron Electron 1 +1 1 1 -1 1 -1 Atoms have a small central nucleus, which is made up of protons and neutrons, around which there are electrons

Label the atom Atoms have no electrical charge because the number of positive particles (protons) is the same as the number of negative particles (electrons) so they cancel each other out! Eg, Be: 4 protons (+4); 4 electrons (-4) = 0 charge (neutral)

Mass number and Atomic number Number of protons + Number of neutrons 9 Atomic Number = Number of protons Number of electrons 4 Beryllium has: 4 protons 4 electrons How many neutrons?

Electronic structure 1st shell holds a maximum of 2 electrons 2nd shell holds a maximum of 8 electrons 3rd shell holds a maximum of 8 electrons Each level/shell has a maximum number of electrons it can hold Electrons will fill the levels nearer to the nucleus first This is and atom of Argon, it has an electronic structure of 2,8,8

Group 1 – Alkali metals Elements in the same group in the periodic table have the same number of electrons in their highest energy level (outer shell) which gives them similar chemical properties Alkalis metals react strongly with water and oxygen

Noble gases - Group 8 elements Noble gases are unreactive because their atoms have stable arrangements of electrons They have eight electrons in their outer energy level – except for Helium, which only has 2 electrons