Unit C4: Chemical Patterns

REVISION

UNIT C4: CHEMICAL PATTERNS

The Periodic Table; Alkali metals and Halogens 

Arrangement of elements
- Proton/Atomic number at the bottom of element
- Relative Atomic Mass number shown above element
- Metals are on the left - Most elements are metals- Non-metals on the right
- Group number shown across the top of the table
- Elements become less metallic from left to right

 

Alkali Metals - Group 1
-  Soft metals, React with oxygen and water in the air - Shiny metal tarnishes
- Reactivity increases further down group 1
- Highly reactive - handle with care - Use gloves
- Low melting/boiling points
- Metals become softer as you go down the group
- Dissolve in water to form alkaline solutions
- Universal indicator - purple 
- Corrosive 
Alkali metal + cold water = Hydrogen and Metal hydroxide 
Alkali metal + Chlorine gas = Metal chloride

Halogens - Group 7
- Halogens are Diatomic - consist of a pair of atoms 
- Low melting/boiling points - increase down the group
- At room temp, Fluorine + Chlorine are gases, Bromine is liquid, Iodine and Astatine are solid
- Colour darkens further down the group: Fluorine = pale yellow, Bromine = Red/brown
- Reactivity decreased further down the group - Displacement reactions - More reactive halogen takes the place of the less reactive halogen
- Bleaching Agents and kill bacteria
Metal + Halogen = Metal Halide