Taylor’s Notes Periodic Table and Group Chemistry
Groups, Periods and the Periodic Table
Elements in the periodic table are organised in order of increasing atomic number
The group of an element tells you how many outer shell electrons there are
Elements In the same group have chemical properties that are similar because they have the same number of electrons in their
outer shell The number of outer shell electrons determines chemical reactivity
The period of an element tells you how many shells of electrons it has
An atom has the electronic configuration: 2,8,18,18,8,1 This element is in group 1 and period 6
Group 0
Elements in group 0 have a full outer shell of electrons
This means that they are described as being inert as they are very unreactive and don’t need to gain or lose any electrons to
have a full outer shell of electrons
Boiling points of Group 0 elements increases down the group because the atoms become larger The intermolecular forces
between the atoms become stronger More energy is needed to overcome them
Group 1 The Alkali Metals
Elements in group 1 have 1 outer shell electron
This means when they react, they lose one electron to form an ion with a 1+ (positive) charge
Metal + Water Metal hydroxide and Hydrogen
Potassium is more reactive than sodium because potassium has the electronic configuration: 2,8,8,1 compared to sodium that
has the electronic configuration: 2,8,1
As we go down the group, the outer shell electron is further from the nucleus, it is therefore less attracted to the nucleus and so
it is lost easier Making potassium more reactive than sodium
Observation Lithium (Li) Sodium (Na) Potassium (K)
Floats on Water Yes Yes Yes
Disappears Yes Yes Yes
Melts into a ball No Yes Yes
Flame No No Yes (Lilac Flame)
Moves across the water Slowly Quickly Very Quickly
Fizzing Steady Rapid Violent
Group 7 The Halogens
Elements in Group 7 have 7 outer shell electrons
This means that when they react, they gain one electron to form an ion with a 1- (negative) charge
Halogens as elements are diatomic molecules and have trends in physical properties down the group:
They become darker in colour
Their melting/boiling points increase (hence the change from gas to liquid to solid down the group)
Name Formula Colour Physical State at r.t.p Colour in Solution
Fluorine F2 Yellow Gas N/A
Chlorine Cl2 Green Gas Pale Yellow
Bromine Br2 Red/Brown Liquid Orange
Iodine I2 Dark Grey Solid Dark Reddish Brown
Astatine At2 Black Solid N/A
Fluorine is more reactive than chlorine because fluorine has the electronic configuration: 2,7 compared to chlorine that has the
electronic configuration: 2,8,7
As we go down the group, the electron gained is further from the nucleus, it is therefore less attracted to the nucleus and so it is
harder to gain the electron
Groups, Periods and the Periodic Table
Elements in the periodic table are organised in order of increasing atomic number
The group of an element tells you how many outer shell electrons there are
Elements In the same group have chemical properties that are similar because they have the same number of electrons in their
outer shell The number of outer shell electrons determines chemical reactivity
The period of an element tells you how many shells of electrons it has
An atom has the electronic configuration: 2,8,18,18,8,1 This element is in group 1 and period 6
Group 0
Elements in group 0 have a full outer shell of electrons
This means that they are described as being inert as they are very unreactive and don’t need to gain or lose any electrons to
have a full outer shell of electrons
Boiling points of Group 0 elements increases down the group because the atoms become larger The intermolecular forces
between the atoms become stronger More energy is needed to overcome them
Group 1 The Alkali Metals
Elements in group 1 have 1 outer shell electron
This means when they react, they lose one electron to form an ion with a 1+ (positive) charge
Metal + Water Metal hydroxide and Hydrogen
Potassium is more reactive than sodium because potassium has the electronic configuration: 2,8,8,1 compared to sodium that
has the electronic configuration: 2,8,1
As we go down the group, the outer shell electron is further from the nucleus, it is therefore less attracted to the nucleus and so
it is lost easier Making potassium more reactive than sodium
Observation Lithium (Li) Sodium (Na) Potassium (K)
Floats on Water Yes Yes Yes
Disappears Yes Yes Yes
Melts into a ball No Yes Yes
Flame No No Yes (Lilac Flame)
Moves across the water Slowly Quickly Very Quickly
Fizzing Steady Rapid Violent
Group 7 The Halogens
Elements in Group 7 have 7 outer shell electrons
This means that when they react, they gain one electron to form an ion with a 1- (negative) charge
Halogens as elements are diatomic molecules and have trends in physical properties down the group:
They become darker in colour
Their melting/boiling points increase (hence the change from gas to liquid to solid down the group)
Name Formula Colour Physical State at r.t.p Colour in Solution
Fluorine F2 Yellow Gas N/A
Chlorine Cl2 Green Gas Pale Yellow
Bromine Br2 Red/Brown Liquid Orange
Iodine I2 Dark Grey Solid Dark Reddish Brown
Astatine At2 Black Solid N/A
Fluorine is more reactive than chlorine because fluorine has the electronic configuration: 2,7 compared to chlorine that has the
electronic configuration: 2,8,7
As we go down the group, the electron gained is further from the nucleus, it is therefore less attracted to the nucleus and so it is
harder to gain the electron
