Group 2 and 7 Flashcards
what factors affect the ionisation energies of the alkali and alkaline earth metals?
size of the ion and charge of the ion
size of the ion ….. down group 2, why
increases, due to more shielding and less nuclear attraction
group 2 metal + water
metal hydroxide + hydrogen
group 2 metal + oxygen
metal oxide
group 2 metal + chlorine
metal chloride
reactivity of group 2 metal oxides …… down the group
increases
group 2 metal oxide + water
metal hydroxide
group 2 metal oxide + acid
salt + water
group 2 metal hydroxide + acid
salt + water
solubility of group 2 metal hydroxides ….. down the group
increases
magnesium hydroxide uses
as a laxative or for indigestion
solubility of group 2 metal sulphates ……. down the group
decreases
barium sulphate uses
barium meal to cause contrast in x rays
Thermal stability
a measure of resistance to thermal decomposition.
Thermal decomposition
when a substance breaks down when heated.
Polarizing power of a cation
its ability to pull the electrons from the anion into the space between the ions
What 2 things affect polarising power?
size of the ion, charge density
how does a cation polarise a carbonate
distorts the carbonate ion. This weakens the C-O bond
thermally stability of group 2 metal carbonates …….. down the group, why?
increases due to decreased charge density so decreased polarisation of the carbonate ion
thermal decomposition of a group 2 metal carbonate forms
metal oxide + carbon dioxide
fluorine properties
pale yellow gas at room temperature
chlorine properties
pale green gas at room temperature
bromine properties
brown liquid at room temperature
iodine properties
black/grey solid at room temperature
oxidising power of halogens ……. down the group, why
decreases, due to less nuclear attraction from shielding so harder to attract electrons to accept
reducing power of halide ions …… down the group, why
increases, due to less nuclear attraction from shielding so requires less energy to donate an electron
Disproportionation
the same atom is simultaneously reduced and oxidised
Cl2 + H2O
HCl + HOCl
Cl2 + NaOH (cold and dilute)
NaCl + NaClO + H2O
3Cl2 + 6NaOH (hot and concentrated)
5NaCl + NaClO3 + 3H2O
Li+ flame test
crimson
Na+ flame test
Yellow
K+ flame test
lilac
Ca2+ flame test
red
Ba2+ flame test
green
Al3+ with NaOH
white ppt, dissolves in excess
Ca2+ with NaOH
white ppt, does not dissolve in excess
Mg2+ with NaOH
white ppt, does not dissolve in excess
Cu2+ with NaOH
pale blue ppt, does not dissolve in excess
Fe2+ with NaOH
pale green ppt which turns brown when left, does not dissolve in excess
Fe3+ with NaOH
brown ppt, does not dissolve in excess
what is used to clean nichrome wire for flame test
concentrated hydrochloric acid
where should you hold the wire in a flame test
in the edge of the flame
Cl-, Br- and I- colour ppt in silver nitrate
Cl- = white
Br- = cream
I-= yellow
positive carbonate test will
turn limewater cloudy
positive nitrate test will
turn red litmus paper blue with aluminium powder and sodium hydroxide
sulphate test with dilute hydrochloric acid and barium sulphate will form
white precipitate
why are flame test colours formed
heat energy excites electrons to a new energy level, a photon is released when they fall back down. This photon directly relates to the wavelength of visible light.
