Halogens Flashcards
What are the halogens?
Highly reactive non-metals.
What do halogens exist as?
Diatomic molecules (with single covalent bonds)
What ion do halogens form?
1- ion
Why does the atomic radius of group 7 elements increase down the group?
Additional electron shells
How/why does electronegativity vary down group 7?
It decreases- atomic radius and electron shielding increases so electrons in the outer shells are less attracted to the nucleus.
What type of molecule are group 7 elements and what intermolecular forces do they experience?
Simple covalent molecules- weak london forces
How does the strength of the london forces vary down group 2?
It increases as the relative atomic mass of the molecules increases
How do the melting and boiling points vary down group 7?
Melting points and boiling points increase down the group.
What state are the first 4 halogens at room temperature?
F2 = pale yellow gas
Cl2 = pale green gas
Br2 = red/brown liquid
I2 = dark grey solid
Why does reactivity down group 7 decrease?
As atomic radius increases, the nuclear attraction is weakened by additional shielding, so it is harder to attract the outer electron it needs.
What kind of agents are the halogens?
Oxidising agents - they accept electrons from species being oxidised
How does their oxidising power vary down the group?
It decreases - greater shielding and greater atomic radius.
How does their oxidising power vary down the group?
It decreases - greater shielding and greater atomic radius.
What kind of agents are halide ions?
They are good reducing agents.
Why does the halide ions reducing power increase down the group?
Electrons are easier to lose from the larger jobs since there is larger shielding and a larger atomic radius so there is a weaker attraction between the nucleus and outer electrons.
What is formed when NaF and sulfuric acid react?
NaHSO4 + HF
(Sodium bisulphate)
HF as misty fume
What halogen can disproportionate?
Chlorine
What is the equation for the disproportionation of chlorine?
Cl2 + H2O —> ClO- + Cl - + 2H+
What is the disproportionation of chlorine used for?
Water treatment where chlorine is used in small quantities to kill bacteria
What is the risk of chlorine disproportionation?
Chlorine can be toxic
What is the equation for the reaction of sodium hydroxide and chlorine? (Production of bleach)
NaOH + Cl2 —> NaCl + NaClO + H2O
What colour precipitate are all metal
Chlorides?
White
What do hydrogen halides form when reacted with ammonia gas?
Ammonium salts ( in an acid-base reaction)
What do hydrogen halides form when reacted with water?
Dilute acids.
In solution, what ions are formed when hydrogen halides react with water?
(Acids dissociate)
Hydroxonium ion (H3O+) and a halide ion
(Acidic solution)
