Chemistry

atomic number: the number of protons in an element

mass number: number of protons plus number of neutrons in an element

isotope: contains the same number of protons but differs in nuetrons, chemically identical.

ion: an atom which has lost or gained electrons to become a charged species. When metals lose electrons they bcome cations, when non metals gain electrons they become anions.

gamma radiation: an electromagnetic wave, highly penetrating , can mutate DNA.

relative isotipic mass: the mass of an isotope of an atom compared to one twelth of mass of an atom of carbon - 12

relative atomic mass: then mean mass of an atom and it's isotopes compared to one twelfth of an atom of c-12

ionisation energy: energy needed to rip an electron away from a metal leaving a posotive ion when in gaseous state.

Flourine:

State at room temp - pale yellow gas

Tm: -220 

Tb: -188

volatility - yes due to low van Der Waals between mollecules.

Chlorine:

state at room temp - green gas

Tm: -101

Tb: - 35

volatility - yes, low VDW's between mollecules.

Bromine:

state at room temp - orange liquid

Tm: -7

Tb: 59

volatility - yes despite increased VDW'S Br2 liquid becomes Br2 gas easily- VDW'S still low enough

Iodine:

state at room temp - shiny grey solid

Tm: 114

Tb: 184

volatility - no, increased VDW's, more energy needed to overcome attracins between I2 mollcules.

presence of a permanant dipole means there will be an attraction to another polar mollecule. 

This extra attraction means you will need more energy to loosen bond, so melting point increases.