patterns in the periodic table

• there are a total of 7 periods
• the elements in the same period have the same number of electron shells
• elements in the same group has the same number of valence electron
• there are 18 groups
• elements in the same group have similar chemical properties as they have the same number of valence electrons
• group 17; 7 valence electrons as transition metals are not counted
• from left to right of the periodic table, there is a decrease in metal properties and increase in non metal properties
• going down a group, there's an increase in metal properties but decrease in non metal properties
• going down the group, atom loses its outermost electrons easily and size of atoms increases
• group 1 metals are called alkali
• properties of alkali


  soft, floats on water, highly reactive so store in oil to prevent contact with oxygen and water vapour
• going down group 1, reactivity increases. melting/boiling point and density decreases
• alkali metals usually form white coloured ionic compounds
• alkali metal + water -> alkali + hydrogen
• alkali metal reacts with water to form an alkali and hydrogen
• halogens are diatomic molecules
• group 17 elements are called halogens
• reactivity decreases down group 17 while melting/boiling point increases
• color of halogen becomes darker