shapes of molecules and ions Flashcards
predict with reasons the bond angle in ammonia
e pairs repel, must get as far apart as possible, lp repel more than bp, so bp get closer together, ammonia has 1lp so bond angle is reduced to 107
shape and bond angle of water
non-linear, 104.5, 2lp 2bp
shape and bond angle of ammonia
trigonal pyramidal, 107, 1lp 3bp
shape and bond angle of methane
tetrahedral, 109.5, 0lp 4bp
model mark scheme
name, bond angle, n bp lp where relevant, lp>bp so bp closer/ bp repel equally (dep on q)
give n example of a simple covalent molecule which has all bond angles equal to 90’
.
By reference to all the atoms involved explain, in terms of electrons, how Na2S is formed from its atoms.
electron transfer from Na to S
1 e from each of 2 Na atoms
Predict the shape of the AlH4- ion. Explain why it has this shape.
tetrahedral, =repulsion, bw 4 bps
A bond in AlH4- can be represented by H → Al
diative/ coordinate
lone pair
donated from H- to Al
Sodium reacts with ammonia to form the compound NaNH2 which contains the NH2– ion.
Draw the shape of the NH2– ion, including any lone pairs of electrons.
Name the shape made by the three atoms in the NH2– ion.
bent
labelled atoms
lone pairs
bent
ICl3
3bp, 2lp, trigonal pyramidal
NO2-
2bp( double bonds), 1lp, bent
XeF2
2bp, 3lp bent
H30+
3bp, 1lp, trig pry 107
ClF3
3bp, 2lp, trig pry
XeF4
4bp, 2lp, sq planar 90’/ sq base pyr 85
describe and draw the bonding in CS2
covalent,
every lone pair reduces the bond angle by
2.5
what does EPR enable use to predict
arragement of e pairs around a central atom of unfamiliar molecules and ions
bond angle and shape of an ammonium ion
109.5, tetrahedral
carbonate, nitrate ions
both have 3 regions of e density so trig planar 120
sulfate ion
have 4 centres of e density around central atom so tet 109.5
octrahedral shape
6bp, 90
which e pairs repel more strongly
lps
predict with reasons bond angles in F3BNH3
all 109.5, boron and nitrgoen now have four bonded electrons around boron and nitrogen
