Why electronegativity decreases down the group:
-more shells and more shielding
-weaker attraction between nucleus and bonding pair of electrons
Test for ammonium ions
-warm with NaOH
-turns damp red litmus paper blue at mouth of tube
Test for Fluoride ion
-bubbles of gas an colourless solution when reacted with acidified silver nitrate solution
-white precipitate formed when gas (carbon dioxide) bubbled through calcium hydroxide
Test for chloride ions
-nitric acid then silver nitrate= white precipitate
-precipitate dissolves in dilute ammonia
Test for bromide ions
-nitric acid then silver nitrate= cream precipitate
-precipitate remains in dilute ammonia but dissolves in conc ammonia
Test for iodide ions
-nitric acid and silver nitrate=pale yellow precipitate
-precipitate remains in dilute and conc ammonia
Observation when NaCl reacts with conc sulfuric acid
Steamy fumes (HCl) turn damp blue litmus paper red
Observation when NaBr reacts with conc sulfuric acid
-sulfur dioxide, choking gas, turns orange dichromate paper green
-S is yellow solid
Observation when NaI reacts with conc sulfuric acid
Hydrogen sulfide, pungent odour, turns lead ethanoate paper black
-purple vapour from iodine
Observation when iodine displaces bromine
brown solution
Observation when bromine/iodine displace chlorine
brown solution
