Topic 6 Flashcards
What are group 1 metals also referred to as?
Alkali metals
Why do alkali metals have similar chemical properties?
Because they all have one outer electron
Do alkali metals form ionic compounds or covalent bonds?
They form ionic compounds
Name 2 physical properties of Group 1 metals? (LS)
- Lower melting and boiling points
2. Very soft - can be cut with a knife
Why are group 1 metals very reactive- (outer shell)
Because it is easy for them to lose an electron to gain a full outer shell
Why do group 1 metals are get more reactive further down the group?
The electrons are further away from the nucleus which means it can lose its outer electron more easily as the electron would be less attracted to the nucleus
What happens when alkali metals are put in water?
They react vigorously and a hydroxide and hydrogen gas is produced
Predict what would happen if you reacted lithium with water?
The lithium would move around the surface, fizzing furiously
Predict what would happen if you react Sodium and Potassium with water
They would do the same as lithium but they would also melt in the heat of the reaction. Potassium gets hot enough to ignite the hydrogen gas being produced.
Predict what would happen if you react caesium and rubidium with water?
They would cause a huge explosion
What are group 7 elements also known as?
Halogens
Why do group 7 elements have similar chemical properties?
They all have 7 electrons in their outer shell
What do halogens exist as? (Type of molecule?)
They exist as diatomic molecules. They share a pair of electrons in a covalent bond so both atoms can gain a full outer shell. (e.g Cl2)
What happens to the melting and boiling points of the halogens as you go down the group?
They increase
What is Chlorine like in room temp?
- fairly reactive
- Poisonous
- Green gas
What is Bromine like as a liquid?
- Poisonous
2. red-brownish
What is Bromine like as a gas?
Gives off an orange vapor at room temp
What is iodine like as a solid?
Dark grey crystalline solid
What is iodine like as a gas?
Gives off purple vapor when heated
Predict what astatine would be like at room temp?
A black solid with a melting point of around 300
How do you test for chlorine?
By holding a piece of damp blue litmus paper over a gas, and if there is chlorine present, the paper would turn white.
Why may the litmus paper turn red for a moment when testing for chlorine?
This is because a solution of chlorine is acidic
What is the trend in reactivity as you go down group 7?
Reactivity decreases
Why does reactivity decrease as you go down group 7?
- A halogen atom needs to gain one electron to get a full outer shell
- The easier it is to gain the electron, the more reactive the element would be
- As you move further away from the nucleus, it gets harder to attract the extra electron. This means halogens would be less reactive as you go down the group
What can halogens and metals react to make?
Metal halides e.g. sodium and chloride make NaCl
What can hydrogen and halogens react to form?
Hydrogen halides e.g. hydrogen and chlorine to make hydrogen chloride
What are some properties of hydrogen halides?
- They’re soluble
2. They can dissolve in water to form acidic solutions e.g. HCl in water
Would halogens have similar or different properties and what would this mean about halogens further down in the group?
They have similar properties, meaning we can predict the properties of astatine and fluorine
What would happen in a displacement reaction between a halogen and halide ions?
The more reactive element displaces the less reactive element and the halide ions may be oxidized (lose electrons) whilst the halogens may be reduced (gain electrons)
Describe how you would carry out a halogen displacement reaction?
- Measure amount of halide salt solution in a test tube
- Add a few drops of a halogen solution to it and shake gently
- If there is a colour change, a reaction has happened and the halogen has displaced the halide ion. If no reaction happens, there wont be a colour change and the halogen is less reactive than the halide and so cant replace it
- Use different combinations of hydrogen and halide ions
What would you expect to see if you mixed potassium chloride with chlorine water? (both colourless and aqueous)
No reaction
What would you expect to see if you mixed potassium bromide with chlorine water?
An orange solution formed. (bromine) as the bromide ions are oxidised to bromine
What would you expect to see if you mixed chlorine water with potassium iodide?
A brown solution formed as the iodide ions are oxidised to Iodine
What would you expect to see if you mixed bromine water with Potassium iodide?
A brown solution formed as the iodide ions are oxidised to iodine
What would you expect to see if you mixed Potassium bromide with iodine water?
No reaction
Judging by group 7’s reactivity, how would you think Astatine would react?
It won’t react as it cant displace any other element
What are group 0 elements also known as?
Noble gases
What are some properties of Noble gases?
- They are inert
- Colourless
- Non-flammable as they’re inert
What colour gases are group 0 at room temperature?
They are colourless at room temperature
Why are noble gases inert
Because they already have a full outer shell
Are noble gases monatomic or diatomic?
They are monatomic (single atoms)
How does argon protect filament lamps?
As its non-flammable it stops the very hot filament from burning up
How does argon, krypton, and xenon help in flash photography (burn)
It stops the flash filament from burning up during the high temperature flashes
How are argon and helium used to protect metals (inert)
They protect metals that are being welded as the inert atmosphere stops the hot metal reacting with oxygen
How is Helium used in airships and balloons?
It has a lower density than air, so it makes balloons float. It is also non-flammable which makes it safer to use than hydrogen
What is the trend in boiling/melting point and density as you move down group 0?
It increases as you move down the group
