C2.4 - R* Group 7 - the halogens Flashcards
What are the group 7 elements called?
The group 7 elements are called the halogens
The group 7 elements
The group 7 elements are:
- Fluorine
- Chlorine
- Bromine
- Iodine
- Astatine
Halogens
The halogens are a group of toxic non-metals that have:
- Coloured vapours
- Fairly typical properties of non-metals
What are the fairly typical properties of non-metals?
The fairly typical properties of non-metals:
1. They have low melting points and boiling points
Their melting and boiling points increase going down the group
2. They are poor conductors of heat and electricity
As elements, what do the halogens all exist as?
As elements, the halogens all exist as diatomic molecules, made up of pairs of atoms
The electronic structure of the halogens determines the way they react with other elements.
How many electrons do they have in their outermost shell (highest energy level)?
The halogens have 7 electrons in their outermost shell (highest energy level)
What happens when halogens react with non-metals?
When halogens react with non-metals, they gain an extra electron by sharing a pair of electrons with another atom
How fluorine reacts with hydrogen
Fluorine reacts explosively with hydrogen
How chlorine reacts with hydrogen
Chlorine reacts explosively with hydrogen, in sunlight
How bromine reacts with hydrogen
Bromine reacts with hydrogen, only:
- At over 300 degrees Celsius
- In the presence of a platinum catalyst
How iodine reacts with hydrogen
Iodine reacts with hydrogen, only:
- At over 300 degrees Celsius
- In the presence of a platinum catalyst
Examples of halogens reacting with metals, when the halogen atoms gain a single electron to give them a stable arrangement of electrons and form ions with a 1- charge
Examples of halogens reacting with metals, when the halogen atoms gain a single electron to give them a stable arrangement of electrons and form ions with a 1- charge are:
- Sodium chloride
- Iron (III) bromide
To check the order of reactivity of the halogens, you can do what?
To check the order of reactivity of the halogens, you can carry out test tube reactions
What rule do you use when carrying out test tube reactions to check the order of reactivity of the halogens?
The rule you use when carrying out test tube reactions to check the order of reactivity of the halogens is that a more reactive halogen will displace a less reactive halogen from solutions of its salts
When carrying test tube reactions to check the order of reactivity of the halogens, you use what?
When carrying test tube reactions to check the order of reactivity of the halogens, you use solutions of:
- The halogens
- Their salts in water
When carrying out test tube reactions to check the order of reactivity of the halogens, what will the colour of the solution after mixing be due to?
When carrying out test tube reactions to check the order of reactivity of the halogens, the colour of the solution after mixing will be due to the less reactive of the pair of halogens
What will chlorine (aq) be in solution?
Chlorine (aq) will be very pale green in solution
What will bromine (aq) be in solution?
Bromine (aq) will be yellow in solution
What will iodine (aq) be in solution?
Iodine (aq) will be darker red/brown colour
Why can you not carry out fluorine reactions in aqueous solutions, even though you know it would displace all of the other halogens as it is the most reactive?
You cannot carry out fluorine reactions in aqueous solutions, even though you know it would displace all of the other halogens as it is the most reactive, because it reacts so violently with water
Describe fluorine
Fluorine is a very reactive, poisonous yellow gas
Describe chlorine
Chlorine is a fairly reactive, poisonous, dense green gas
Describe bromine
Bromine is a poisonous, dense red-brown volatile liquid
Describe iodine
Iodine is a:
1. Dark grey crystalline solid
Or,
2. Purple vapour
As elements, the halogens all exist as molecules made up of pairs of atoms - diatomic molecules.
How are the atoms in each pair joined to each other?
The atoms in each pair are joined to each other by a covalent bond
When carrying test tube reactions to check the order of reactivity of the halogens, you use solutions of the halogens and their salts in water.
Example
For example, chlorine dissolved in water, mixed with potassium bromide solution
The trends as you go down group 7
The trends as you go down group 7 are:
- Reactivity decreases
- Melting and boiling points increase
- Relative atomic masses increase
How do all the group 7 elements react?
All the group 7 elements react in similar ways
Why do all the group 7 elements react in similar ways?
All the group 7 elements react in similar ways, because they all have 7 electrons in their outer shell
What can halogen atoms do, to achieve a full outer shell?
Halogen atoms can share electrons to achieve a full outer shell
Halogen atoms can share electrons, via covalent bonding with other non-metals, to achieve a full outer shell.
Example
For example: 1. HCl 2. HF 3. CCl4 contain covalent bonds
What do the compounds that form when halogens react with non-metals all have?
The compounds that form when halogens react with non-metals all have simple molecular structures
What do the compounds that form when halogens react with metals all have?
The compounds that form when halogens react with metals all have ionic structures
What can a displacement reaction occur between?
A displacement reaction can occur between:
- A more reactive halogen
- The salt of a less reactive one
The electronic structure of the halogens determines the way they react with other elements.
The halogens have 7 electrons in their outermost shell (highest energy level), so they need to gain just one more electron to achieve what?
The halogens have 7 electrons in their outermost shell (highest energy level), so they need to gain just one more electron to achieve the stable electronic structure of a noble gas
When halogens react with non-metals, they gain an extra electron by sharing a pair of electrons with another atom.
Examples
For example:
- Hydrogen
- Oxygen
Fluorine reacts explosively with hydrogen, even what?
Fluorine reacts explosively with hydrogen, even:
- At -200 degrees Celsius
- In the dark
Chlorine reacts explosively with hydrogen, in sunlight, but how in the dark?
Chlorine reacts explosively with hydrogen, in sunlight, but slowly in the dark
Iodine reacts with hydrogen, only at over 300 degrees Celsius and in the presence of a platinum catalyst.
It is what?
The reaction of iodine and hydrogen, at over 300 degrees and in the presence of a platinum catalyst is:
- Very slow
- Reversible
Examples of halogens reacting with metals, when the halogen atoms gain a single electron to give them a stable arrangement of electrons and form ions with a 1- charge are Sodium chloride and iron (III) bromide.
These are what compounds?
- Sodium chloride
- Iron (III) bromide
are ionic compounds
When carrying out test tube reactions to check the order of reactivity of the halogens, the colour of the solution after mixing will be due to the less reactive of the pair of halogens, which is what?
When carrying out test tube reactions to check the order of reactivity of the halogens, the colour of the solution after mixing will be due to the less reactive of the pair of halogens, which is left in solution as the aqueous molecule
Halogen atoms can share electrons, via what, to achieve a full outer shell?
Halogen atoms can share electrons, via covalent bonding with other non-metals, to achieve a full outer shell
