8.2 - The Halogens Flashcards
What do the halogens exist as on earth ?
Stable halide ions
What is the trend in boiling points ?
- boiling point increases down the group
- halogens are diatomic molecules at room temperature
- the halogens are simple molecular structure with weak London forces between the diatomic molecules caused by instantaneous dipole-induced forces
- more electrons in a molecule = the greater the instantaneous dipole- induced dipole forces
- larger the molecule = the stronger the London forces between molecules
- as you go down the group gets more difficult to separate the molecules and the boiling point increases
What happens to the reactivity of the halogens as you go down the group ?
- decreases as you go down the group
- atomic radius increases
- more inner shells = shielding increases
- less nuclear attraction to capture an electron from another species
- reactivity decreases
Are halogens reducing agents or oxidising agents ?
- each halogen atom is reduced
- gaining one electron to form a 1- halide ion with the electron configuration of the nearest noble gas
Cl2 + 2e- —-> 2Cl-
Chlorine is reduced
- another species loses electrons to halogen atoms = it is oxidised and the halogen is now known as the oxidising agent because it has oxides another species
What does the F2 appear and state at RTP ?
Pale yellow gas
What does Cl2 appear and state at RTP ?
Pale green gas
What does Br2 appear and state at RTP ?
Red- brown liquid
What does I2 appear and state at RTP ?
Shiny grey - black solid
What does At2 appear and state as in RTP ?
Never been seen before
What is different about fluorine in terms of bond enthalpy ?
- possesses a value to that of iodine
- fluorine atoms are so close together that the lone pair’s of electrons repel each other
- thus weakening the bond
What happens to the atomic radius down the group ?
- it increases because there are more emerged levels of electrons
- the outer energy levels are further from the nucleus
What is meant by a halogen displacement reaction ?
When a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide
What colour is chlorine in potassium chloride (aq) ?
Very pale green solution - no reaction
What is the observation of colour in chlorine in potassium bromide ( aq) ?
Yellow solution
Cl has displaced Br
What is the colour observation for chlorine In potassium iodide (aq) ?
Brown solution
Cl has displaced I
