group 2 and 7 revision Flashcards
group 2 elements act as ___ agents
Reducing agents (they give electrons)
describe the trend in reactivity of the group 2 elements
They Increase in reactivity going DOWN the group
group 2 hydroxides are formed in reactions with water. describe the trend in their solubility
the solubility of group 2 hydroxides increases going DOWN the group. Similar to the reactivity of the elements
explain the trend in reactivity of group two elements
when group 2 elements react they are oxidised loosing two outer electrons.
the further down the group the lower the 1st and 2nd ionisation energies become.
this is because electrons are further from the positive nucleus and because there is an increasing number of electron shells shielding the attraction from the nucleus. There is less NUCLEAR ATTRACTION.
what effect does the solubility of group 2 hydroxides have on the PH of the solution
More soluble Group 2 hydroxides like barium hydroxide give the aqueous solution a higher concentration of OH- ions. This makes it More alkaline giving it a higher PH
What are the some of group two compounds
Calcium hydroxide (lime) is spread on fields to reduce acidity of soil
Magnesium hydroxide and Calcium carbonate are used to treat indigestion by neutralising stomach acid. Ca(OH)2 is not used as it is too alkaline
Barium sulphate used in barium meals to do xrays of stomach
describe and explain the trend in the melting points of group 7 elements
Group 7 elements form simple molecular lattices where molecules are held together by weak induced dipole forces. These forces increase in strength as the number of electrons in each molecule increases ie when the elements get bigger.
describe and explain the trend of the reactivity of group 7 elements
group 7 elements are reduced gaining one electron when they react.
the reactivity of group 7 decreases further down the group as the ability of the nucleus to attract the bonding electron decreases.
this is because there is more shells which screen the attraction of the positive nucleus and more distance which reduces the attraction between electrons and the nucleus. There is less NUCLEAR ATTRACTION.
what are some uses of group 7 elements and compounds
chlorine is used in water treatment to kill bacteria. Chlorine reacts with water to produce chloric(I) acid which kills bacteria. However there is a risk of chlorine forming chlorinated hydrocarbons which can cause cancer.
