Group 7 consists of highly reactive non-metals called halogens.

Some main properties of the first 4 elements in group 7 are listed below.

halogen | formula | colour | physical state | electronic structure |
---|---|---|---|---|

fluorine | F_{2} |
pale yellow | gas | 1s^{2}2s^{2}2p^{5} |

chlorine | Cl_{2} |
green | gas | 1s^{2}2s^{2}2p^{6}3s^{2}3p^{5} |

bromine | Br_{2} |
red-brown | liquid | 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{5} |

iodine | I_{2} |
grey | solid | 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{5} |

### TrendsEdit

Boiling and melting points increase as you go down the group. This is because the strength of the van der Waals forces increase since the atoms have more electrons as you descend the group. This trend is highlighted by the fact that the physical state of the halogens change from Fluorine (gaseous) to Iodine (solid) down the group. Volatility decreases down the group as the boiling points increase.