Topic 8 Flashcards
What metals are in group 1
Alkali
Physical properties of alkali metals
Good conductors if heat and electricity
Shiny when freshly cut
However compared to most other metals
Are soft - cut with a knife
Have relatively low melting points (all solid)
Alkali + water ->
Alkaline metal hydroxide + hydrogen
Reactivity of alkali metals
Increases down group
Lithium fizzes steadily
Sodium melts into a ball from heat released in the reaction and fizzes rapidly
Density of alkali metals
Lithium, sodium and potassium are less dense than water so they float
Storage of alkali metals
Lithium sodium and potassium are stored in oil this is to keep and water away
Rubidium is placed below potassium in the periodic table. Predict what is seen in the reaction of rubidium with water.
Rubidium will react very vigorously with water, producing sparks and bursting into flames explosively
Explain why sodium is more reactive than lithium
Sodium atoms are larger than lithium atoms. So the outer electron in a sodium atom is further from the nucleus than the outer electron in a lithium atom
This means that the force of attraction is weaker
So the outer electron is lost more easily from sodium than lithium
What are the elements in group 7 called
Halogens
Colour of fluorine
Pale yellow
Chlorine colour
Yellow-green
Bromine colour
Red-brown
Iodine colour
Dark grey
Melting and boiling points going down group 7
Melting point increase
Boiling point increase
When simple molecular forces melt or boil
Wean intermolecular forces are overcome
The strong covalent bonds joining atoms together in each molecule do not break
Going down group 7
The intermolecular forces between molecules become stronger
More heat energy is needed to overcome these forces
Metal + halogen
Metal hallide
In reactions with metals
Halogen atoms gain electrons and are reduced
How many atoms do halogens have in there outer shell
7
Going down group 7:
The outer shell gets further from the nucleus
There is more shielding by inner electrons
The force of attraction between the nucleus and outer shell electrons gets weaker
Electrons are gained less easily
The elements become less reactive
How can you demonstrate a displacement reaction
By adding a halogen solution to a metal halide solution, then seeing if the mixture darkens for example
Chlorine in ‘chlorine water’ displaced from aqueous sodium bromide solution
What are redox reactions
Halogen displacement
Where are the noble gases
Group 0
The noble gases are chemically
Inert
Noble gases have a lack of reactivity because
Their atoms have full outer shells of electrons so they have no tendency to lose gain or share electrons
Use of helium
Lifting gas in party balloons and airships
Reason for helium’s use
Helium is less dense than air so the balloons and airships rise
It is non-flammable so does not ignite
Helium properties needed
Low density
Inertness
Argon krypton and xenon uses
Filling gas in filament lamps
Property needed in argon krypton and xenon
Inertness
Reason for use (argon krypton xenon)
The metal filament becomes hot enough to glow
The inert gases stop it burning away
Argon use
Shield gas during welding
Property needed for argon
Inertness
Reason for argon use
Argon is gender than air so it keeps air away from the metal
It is inert so the metal does not oxidise
Colliding particles
For s reaction to happen:
Reactant particles must collide with each other and
The collisions must have enough energy
What’s activation energy
The minimum energy needed by a reaction particles for a reaction to happen
A successful collision has the activation energy of more
Rate and time o reactions
The greater the rate of reaction the lower the reaction time
A fast reaction happens in a short time such as combustion
A slow reaction happens over a long time such as rusting
Concentration and pressure
The rate of reaction increases if the concentration of a dissolved reactant increased or if the pressure of a reacting gas increases
There are more particles in the same volume
The frequency of successful collisions increases
Temperature
The rate of reaction increases when the temperature increases because the particles gain energy and
The particles move faster
The frequency of collisions increases and the energy of collisions increases so a greater protoitduin of collisions are successful
Surface area : volume ratio
The rate of reaction increases when the sa:v ratio of a solid reactant increases eg when lumps are made into a power
More particles of a reactant are available
The frequency of successful collisions increases
