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Periodic Table - Group 7 Elements
Reactivity of the elements in group 7 decreases down the group. This is because the electrons in the outer shell are further away from the nucleus.

Periodic Table - Group 7 Elements

In GCSE Chemistry students must have a good knowledge of the periodic table. Most UK exam boards still follow the convention that the number of electrons in the outer shell = number of group. Since most schools teach to that convention, we use it in our quizzes. If you study chemistry to higher levels, you will find that this is no longer the case other than for groups 1 and 2.

In this quiz we look at the group 7 elements - the halogens.

Halogens is a combination of ancient Greek words that mean 'salt formers'. This refers to the fact that the group 7 elements will produce salts directly with metals. The combination of sodium and chlorine for example produces sodium chloride - common salt.

Naming the salts formed from the halogens is fairly straightforward: remove the ending -ine and replace it with the ending -ide. So if the halogen iodine reacts with the metal potassium, the salt formed will be potassium iodide.

On the periodic table, the halogens are the last but one group (vertical column), right next to the noble gases. The group number is 7 which indicates that halogen atoms contain seven electrons in the outer shell (energy level). In order to achieve stability and have the same structure as the nearest noble gas, these atoms gain a single electron (rather than losing seven electrons which would take much more energy).

Choose the correct order from top to bottom of group 7.
F, Br, I, At, Cl
At, I, Br, Cl, F
F, Cl, Br, I, At
Br, Cl, I, At, F
It is useful to remember this order of elements as it the patterns of chemical and physical properties of group 7 usually refer to all or part of it
Group 7 elements are also known as...
Alkali metals
Transition elements
Noble gases
From the ancient Greek - halos (salt) and gen (producer)
Reactivity of the elements in group 7 decreases down the group. This is because...
There are more electrons in the outer shell
The electrons in the outer shell are further away from the nucleus
The electrons are closer to the nucleus
There are more electrons in the atom
The halogens react by attracting electrons from other atoms into the outer shell. As you descend the group, the atoms have more shells. These shield incoming electrons from the attractive force of the nucleus making it more difficult for the atoms to react
How many electrons are in the outer shell of the group 7 elements?
At GCSE, the group number gives you the number of outer electrons
Bromine displaces iodine from solution because...
Iodine is more reactive than bromine
Bromine is more reactive than iodine
Bromine is a smaller atom
Iodine has more electrons than bromine
Reactivity of the halogens decreases down the group
Iodine is...
a pale yellow gas
a dense green gas
a dark grey crystalline solid
a dark orange-brown solid
Iodine is poisonous and produces a violet coloured vapour when heated
Halogens exist as molecules made up of pairs of atoms, joined together by covalent bonds. These molecules are known as...
Di = two and atomic = atoms
What type of bonds do group 7 elements form?
Ionic and covalent
Covalent only
Metallic and covalent
Hydrogen and metallic
They form ionic bonds with metals but can also form covalently bonded molecules with other non-metals
Halogens all react with metals. How many electrons do they gain when they undergo this type of reaction?
This gives them the stable electron configuration of the nearest noble gas
Group 7 elements only form what type of ion?
They all gain one electron to fill their outermost electron shell
You can find more about this topic by visiting BBC Bitesize - Groups in the periodic table

Author:  Kate Gardiner

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