inorganic chemistry and the periodic table Flashcards
(42 cards)
group 7 name
characteristics
halogens
diatomic molecules
Why are fluorine and astatine generally ignored out of the halogens?
Fluorine behaves differently to rest of elements and astatine only exists as a radioactive isotope
trend in state down group 7
gas to solid
trend in mp/bp down group 7
increases
trend in electronegativities down group 7
decreases
how London forces are formed between diatomic halogen molecules
identical atoms mean pair of electrons are shared equally between (therefore on average aren’t polar). fluctuations in charge result in a temporary dipole. if molecule on left forms an instantaneous dipole, another dipole is induced on right, producing a force of attraction (instantaneous dipole-induced dipole attraction).
trend in bond strength between atoms in group 7
increases as number of electrons in molecules increases
properties determining electronegativity of an atom
nuclear charge
distance between nucleus and bonding pair
shielding effect
trend in reactivity down group 7
decreases down group w electronegativity
roles of halogens in reactions
act as oxidising agents, gaining electrons to form a negative ion.
due to high electronegativity
most vigorous reactions between group 1 and 2 metals with halogens
elements at bottom of groups 1 and 2 with elements at top of group 7
products of group 1 and 2 metals w halogens
reaction process
salts
ionic salts that are usually white
redox reactions in which halogen acts as oxidising agent
oxidation numbers in reaction between group 1 and 2 metals w halogens
halogen decreases from 0 to -1
metal increases from 0 to +1/+2
way to make halide colors more distinctive
add an organic solvent such as cyclohexane as halogens are more soluble than in water so will dissolve in upper layer where colors will be more distinctive
color of chlorine / bromine/ iodine
Cl» green
Br» orange brown
I»_space; purple
why is chlorine most reactive of halogens?
atom is smaller so outer electrons are closer to nucleus
smallest amount of shells and so shielding is reduced
disproportionation
a reaction in which one element undergoes both oxidation and reduction simultaneously.
reaction of chlorine with water
forms chloric acid and hydrochloric acid
Cl2 +H2O»_space; HCl + HCLO
reaction of chlorine with cold alkali
forms salts of the chloric and hydrochloric acids
sodium chloride and sodium chlorate 1
eg, 2NaOH + Cl2»_space; NaCl + NaClO + H2O
sodium chlorate use
disinfectant, used as main ingredient of bleach.
reaction of chlorine with hot alkali
forms salts of chloride and chlorate 5
eg, 6NaOH + 3Cl2»_space; 5NaCl + NaClO3 + 3H2O
how do halide ions differ from halogen molecules in their reactions
halide ions act as reducing agents in reactions while halogen molecules act as oxidising agents.
reducing power of halide ions as you go down the group
increases
oxidising power of halogen molecules as you go down the group
decreases
