C4 - Group 1, 7 And Flame Tests Flashcards
Describe , generally, the group 1 elements
- all metal
- react vigorously with water to form alkaline solutions
- so they are called alkali metals
What is the general word and symbol equation for group 1 metals reaction with water.
Metal + Water -> Metal Hydroxide + Hydrogen
M + H20 -> 2MOH + H2
Describe the reactivity of sodium, lithium and potassium. Describe their reactions with water
Reactivity : potassium, sodium , lithium
All three metals float, and the hydrogen causes fizzing which pushes the metals around on the surface.
Potassium : melts to form silvery ball, ignites explosively and then burns with lilac flame. Disappears very quickly
Sodium: melts to form silvery ball, disappears quickly
Lithium: keeps its shape, disappears slowly
Why do group 1 elements get more reactive as you go along?
The easier it is for an atom of a group 1 element to lose on electron , the more reactive it is. As you go down the group, there are more shells, and so the outer electrons are more easily given away. This is called oxidation. General word equation : M -> M+ + e-
Why do group 1 elements have similar properties?
When they react, each atom loses its outer electron to become an ion with a single positive charge.
What colour flames do lithium, sodium and potassium give out in flame tests?
Lithium - Red
Sodium - Orange
Potassium - Lilac
How do you carry out a flame test?
A flame test wire, usually a loop of Nichrome alloy wire, is cleaned by dipping it into hydrochloric or nitric acid. It is then held in the blue flame of a Bunsen burner. This is repeated until the flame colour does not change.
It is then dipped into the acid to moisten it, and then held in the solid sample. It is then held in the edge of the blue flame, and the colour is observed.
Describe some uses of chlorine and iodine.
Chlorine:
- sterilise tap water and swimming pool water as if kills harmful bacteria
- used to make pesticides
- used to make plastics like PVC
Iodine:
- used as an antiseptic to sterilise wounds
Describe the coloured states of chlorine, bromine and iodine at room temperature.
- chlorine is a green gas
- bromine is an orange liquid
- iodine is a grey solid
When iodine is warmed it changes easily into a purple vapour.
What happens if group 7 elements react with group 1 elements? General symbol equation?
Clouds of a metal halide are produced. Fluorine - metal fluoride Chlorine - metal chloride Bromine - metal bromide Iodine - metal iodide
2M + X2 -> 2MX
E.g 2Li + I2 -> 2LiI
Why do group 7 elements have similar properties?
- The outer shells of their atoms all contain seven electrons.
- When they react , each atom gains an electron to become a negative ion because they all have 7 electrons in their outer shell.
What is the general balanced symbol equation for the reaction of a group 1 element, M, with a group 7 element, X2? Give an example with lithium and iodine.
2M + X2 -> 2MX
2Li + I2 -> 2LiI
