Group 2 And 7 Elements Flashcards
How many electrons on outermost shell of group 2
2
what do group 2 metals form
ionic compounds where they donate these two outermost electrons (so they act as reducing agents) to become an ion with +2 charge (so they themselves become oxidised)
Going down the group do group 2 elements get more reactive or less
more
what does the first ionisation energy do
the energy needed to remove the first outer electron of an atom
What happens to the size of the elements down group 2
become larger as the outer two electrons occupy a new shell which is further away from the nucleus
What happens to the melting point of the elements down group 2
The melting point of the elements decreases going down the group as the outer electrons get further away from the nucleus
This means that the attraction between the nucleus and the bonding electrons decreases causing a decrease in melting point
what happens as you go down the group to the density of the alkali earth metals
the density of the alkali earth metals drops till Calcium and then increases
What happens when the group 2 metal oxide reacts with water
a group 2 hydroxide is formed
what happens to the solubility of these hydroxides, going down the group
increases.
This means that the concentration of OH- ions increases, increasing the pH of the solution
As a result, going down the group, the alkalinity of the solution formed increases when Group 2 oxides react with water
Magnesium (group 2 metal) reacting with water at room temp
Equation and description
Mg(s) + 2H2O(l) –> Mg(OH)2(aq) + H2(g)
Very slow reaction with Mg. It will take several hours for bubbles of H2 to start to show.
What is Mg(OH)2 (aq) used for
Magnesium Hydroxide can also be called ‘Milk of Magnesia’ and is used as an indigestion remedy to neutralise stomach acid.
Calcium (group 2 metal) reacting with water at room temp
Equation and description
Ca(s) + 2H2O(l) –> Ca(OH)2(aq) + H2(g)
More vigorous reaction with Ca. It will bubble at a fast rate and the mixture will heat up.
Magnesium (group 2 metal) reacting with steam
Equation and description
Mg(s) + H2O(l) –> MgO(s) + H2(g)
reaction more vigorous with steam than water
How soluble is Mg(OH)2
Insoluble
How soluble is Ba(OH)2
Completely dissolves
How soluble is MgSO4
Completely Dissolved
How soluble is BaSO4
Insoluble
What is BaSO4 (Barium Sulfate) used for
Barium Sulfate is very good at absorbing X rays. Feed the patient a ‘Barium Meal’.
Barium Sulfate is highly toxic. However it is perfectly safe to feed to patients because it is so insoluble it cannot dissolve and pass through cell membranes into body tissue
How to test for Sulfate Ions (SO4 2-)
add a solution of Barium Chloride (BaCl2)
no visible change = NO Sulfate ions present
WHITE PRECIPITATE = Sulfate ions present
Group 7 also known as
Halogens
What is the ion of florine called
Fluoride (F-)
Physical property of Fluorine
very pale yellow gas
Physical property of Chlorine
greenish gas.
Physical property of Bromine
orange/brown liquid which vaporizes easily into an orange gas.
Physical property of Iodine
a black solid which vaporises on heating to a purple gas.
What happens to the size of group 7 going down the group
get bigger on descending the group because each additional element has a whole extra electron shell in comparison to the previous element
What are three factors that affect electronegativity
- A greater nuclear charge will withdraw electrons more strongly.
- A shorter atomic radius will also help withdraw electrons more strongly.
- The more shielding will however reduce the amount electrons can be withdrawn.
What intermolecular forces exist between halogens
As they are non-polar diatomic molecules, they only have Van der Waals forces.
What changes the strength of the van de wall forces in group 7
on the size of the molecule
What element in group 7 has the lowest boiling and melting point
F2
What state is Fluorine and chlorine at room temperature
gas
What state is bromine at room temperature
liquid
What state is iodine at room temperature
solid