Group 7 Flashcards
Colour of
F2
Cl2
Br2
I2
pale yellow gas
green / yellow gas
orange / brown liquid
grey / black solid
volatility down group 7
The melting and boiling points of the Group 7 elements increase going down the group which indicates that the elements become less volatile
are halogens metals or non metals and what type of structure
non-metals
simple molecular structures with weak London dispersion forces between the diatomic molecules caused by instantaneous dipole-induced dipole forces
how is an induced dipole formed
a sudden imbalance of electrons in a nonpolar molecule can cause an instantaneous dipole. When this molecule gets close to another non-polar molecule it can induce a dipole as the cloud of electrons repel the electrons in the neighboring molecule to the other side
the more electrons….
the greater the instantaneous dipole-induced dipole forces
Therefore, the larger the molecule the stronger the London dispersion forces between molecules
This is why as you go down the group, it gets more difficult to separate the molecules and the melting and boiling points increase
As it gets more difficult to separate the molecules, the volatility of the halogens decreases going down the group
what is electronegativity
how strongly an atom attracts electrons towards itself in a covalent bond
does electronegativity decrease down group 7
The electronegativity of the halogens decreases going down the group
Going down the group, the atomic radii of the elements increase which means that the outer shells get further away from the nucleus
An ‘incoming’ electron will therefore experience more shielding from the attraction of the positive nuclear charge
The halogens’ ability to accept an electron (their oxidising power) therefore decreases going down the group
reactivity down group 7
atoms become larger so the outer electrons are further away and are therefore more shielded from the positive nucleus
Larger halogen atoms such as iodine will find it more difficult to attract incoming electrons needed to form the 1- ion
Therefore the reactivity decreases down Group 7
how can you prove decrease in reactivity for group 7
react it with hydrogen
characteristics of
fluroine
chlorine
bromine
iodine
very reactive poisonous gas
reactive poisonous gas - pale gas in solution
dense red brown volatile liquid - orange in solution
crystalline sublimes to form purple vapor and dark brown in solution
why can cyclohexane be added
halogens are more soluble in this layer which helps observe the color changes more easily
color of organic layer for bromine and iodine
bromine - yellow-orange
Iodine - purple
describe the reaction of sulfuric acid with halogen
produce toxic gases
These reactions should therefore be carried out in a fume cupboard
H2SO4(l) + X-(aq) → HX(g) + HSO4-(aq)
reaction of sodium chloride and sulfuric acid
H2SO4 (l) + NaCl (s) → HCl (g) + NaHSO4 (s)
The HCl gas produces is seen as white fumes
Reaction of bromide ions with concentrated sulfuric acid
H2SO4 (l) + NaBr (s) → HBr (g) + NaHSO4 (s)
2HBr (g) + H2SO4 (l) → Br2 (g) + SO2 (g) + 2H2O (l)
The bromine is seen as a reddish-brown gas
