chemistry group 7 (halogens)

what are all the halogens

diatomic molecules

increase of electron shells = more electrons = bigger atom/ molecule

melting and boiling point

increases down the group

• increasing intermolecular forces as atoms get bigger

• more energy needed to overcome these forces

fluorine

highly reactive pale yellow gas

most reactive halogen

chlorine

poisonous green gas

bromine

poisonous orange - brown liquid

gives off orange vapour

iodine

grey solid

gives off a purple vapour

group 7 gain an electron -

7 electrons in outer shell

very unstable (reactive)

gain stability once they gain an electron and become 1- ions

reactivity decreases down the group -

down the group, atoms have more electron shells

attraction between nucleus and incoming electron gets weaker

more shells = more shielding

so an electron is less easily gained

displacement reactions -

A displacement reaction occurs when a more reactive

element replaces, or pushes out, a less reactive

element from a compound.

After a displacement reaction, the less reactive

element is now pure and left uncombined.

sodium iodide + bromine

sodium bromide + iodine