REACTIVITY TRENDS Flashcards
(37 cards)
What happens to ionisation and reactivity as you move down group 2
First ionisation energy decreases as atomic radius increases and so reactivity increases as outer electrons are further from the nucleus so attraction is weaker
What happens to nuclear charge as you move down groups and how does this affect ionisation
number of protons in the atom will increase down the group, so nucleus will become more positively charged, however as the atomic radius increases as number of electron shells increases, this overrides the effect of the increased nuclear charge and ionisation energy will still decrease
what happens group 2 metals react with water
they form bases, metal hydroxides in particular
reactions with water down group 2
More reactivity, as atoms are larger so more electron shielding
BERYLIUM DOES NOT REACT WITH WATER
What happens when magnesium reacts with steam
will form magnesium oxide and will react vigorously
what happens when Group 2 elements react with oxygen
they are oxidised (obviously) and will form metal oxides in a redox reaction
state of group 2 oxides and what happens when they react with water
they are white solids
form bases when added to water (hydroxides)
Group 2 hydroxide trends down the group
become more strongly alkaline as they become more soluble and OH- ions are more likely to be released
Neutralisation and example of a group 2 oxide and hydroxide with acid
will form a group 2 salt and water
CaO + 2HCl –> CaCl2 + H2O
Ca(OH)2 + H2SO4 –> CaSO4 + 2H2O
Use of a group 2 hydroxide in nature
Calcium hydroxide is used to neutralise acidic soils to allow some crops or plants to grow if the pH is too low
Use of a group 2 hydroxide in medicine
Magnesium hydroxide is used to neutralise excess stomach acid as will react to form water and a magnesium salt
Trend of boiling points effect on states down group 7
Boiling point increases as London forces increase due to increasing size and mass of atoms
and so physical state goes from gas down to solid as you move down
Electronegativity trend down group 7
decreases as the atoms get larger so electron shielding increases so ability to attract electrons in a covalent bond will decrease
How can displacement reactions of halogens be observed
hexane is added to the aqueous solution and the halogen will dissolve readily in the solvent causing a coloured organic layer to form above the aqueous layer
how are halide ions displaced
more reactive halogen will displace less reactive halide ions
Reactivity of halogens down the group
decreases as for a reaction to occur the halogen will need to gain an electron, as electronegativity decreases down the group, so does reactivity
HALOGENS ARE LESS OXIDISING AS YOU MOVE DOWN THE GROUP AS THEY ARE LESS READILY REDUCED
Reaction of KCl and Cl2 and colour changes
no reaction, aqueous and organic solution are both colourless
Reaction of KBr and Cl2 and colour changes
Chlorine will displace the bromide ions
aqueous solution will turn yellow and the organic solution will turn orange
Reaction of KI and Cl2 and colour changes
Chlorine will displace iodide ions
aqueous solution will go brown and organic layer will be purple
Reaction of KCl / KBr and Br2 and colour changes
no reaction
aqueous solution will be yellow and organic layer will be orange
KI and Br2 reaction
Bromine will displace iodide ions
aqueous will be brown and organic layer will be purple
Reaction of I2 with KCl, KBr, KI
no reactions
aqueous solution will be brown and organic layer will be purple
How to test for halides and corresponding precipitates
Add dilute HNO3 and then AgNO3, the precipitate colour will help identify the halide ion
Cl- will give a white precipitate (AgCl)
Br- will give a cream precipitate (AgBr)
I- will give a yellowy precipitate (AgI)
Why is HNO3 added when testing for halides
to react with any other anions other than halides (to prevent false results)
