chemistry - groups in the periodic table: group 7 (6.6 - 6.13)

what are group 7 elements called?

halogens

6.6 chlorine, bromine, iodine - colour & physical state at room temp.

6.7 chlorine, bromine, iodine - physical properties pattern

chlorine, bromine, iodine = increasing melting/boiling points

6.7 halogens - physical properties pattern (melting/boiling points)

melting/boiling points increase down group - top = lowest, bottom = highest

6.8 chemical test for chlorine

place damp blue litmus paper in chlorine gas

turns red then bleaches white

6.9 chlorine, bromine, iodine - reactions with metals

form metal halides:

• e.g. chlorine + metal → metal chloride

6.9 halogens - reactions with metals pattern

halogen + metal → metal halide

6.10 chlorine, bromine, iodine - reactions with hydrogen then dissolved in water

form hydrogen halides

• e.g. chlorine + hydrogen → hydrogen chloride

dissolve in water to form acidic solutions

• e.g. hydrogen chloride + water → hydrochloric acid

6.10 halogens - reactions with hydrogen then dissolved in water pattern

halogen + hydrogen → hydrogen halide

hydrogen halide + water → hydro(halide) acid

6.11 chlorine, bromine, iodine - relative reactivity shown by displacement reactions with halide ions in aqueous solution

more reactive halogen displaces less reactive halogen from halide compound

• e.g. chlorine + sodium bromide → bromine + sodium chloride

6.11 astatine - displacement reaction with halide ions in aqueous solution

bottom of group 7 = least reactive = won’t displace halide ion

6.12 displacement reactions - redox

redox reaction: one substance oxidised, one reduced

involve transfer of electrons - both oxidation & reduction occur at same time

e.g. chlorine + sodium bromide → bromine + sodium chloride

• chlorine atom → chloride ion (reduction - gains electron)

• bromide ion → bromine atom (oxidation - loses electron)

6.13 explain halogens relative reactivity (electronic configuration)

7 valence electrons - gain 1 electron when react

down group:

• number of electron shells increases

• force of attraction between + nucleus & - valence electron decreases

• shielding increases

• harder to gain electron

• harder to form ions

• reactivity decreases