Bonding And Molecules

Question 1

Ionic bonding

Answer 1

Electrostatic attraction between positive and negative ions
Dot and cross diagrams

Question 2

Ionic structure

Answer 2

Giant ionic lattice

Question 3

Properties of ionic compounds

Answer 3

Solid at room temp - high temp overcome strong electrostatic forces between ions - larger charge high mp
Dissolve in polar solvents such as water charges larger less soluble
Ionic compound conducts when melted or dissolved in water- ions are free to move

Question 4

Covalent bonding

Answer 4

Strong electrostatic attraction between a shared pair of electrons and nuclei of bonded atoms
Orbital overlap
Only localised to one molecule

Question 5

Electron pair repulsion theory

Answer 5

Electrons repel one another so are arranged as far as possible
Lone pairs repel more strongly than bonding pair
This determines the shape

Question 6

Shapes of molecules

Answer 6

Tetrahedral = 109.5
Pyramidal = 107
Non linear = 104.5
Linear = 180
Octahedral =90

Question 7

Electronegativity

Answer 7

The ability of a bonded atom to attract a pair of electrons in a covalent bond

Question 8

Electronegativity trends

Answer 8

Increases across a period nuclear charge increases and the atomic radius decreases
Increases up a group due to greater nuclear charge and its effect on the outermost electron

Question 9

Non polar bonds

Answer 9

When Electronegativity is the same or very similar bonded electron pit is shared equally
Pure covalent bond

Question 10

Polar bonds

Answer 10

Bonded electron pair shared unequally
When one atom has greater Electronegativity than another
Permanent dipole formed

Question 11

Polar molecules

Answer 11

Requires permanent dipoles
Dipoles act in different directions and don’t cancel out
Eg H20
Co2 dipoles cancel each other out

Question 12

Intermolecular forces

Answer 12

Induced dipole dipole (London)
Permanent dipole dipole
Hydrogen bonding
Weakest-> strongest

Question 13

Induced dipole dipole

Answer 13

Movement of electrons produces a changing dipole- forms an instantaneous dipole
This induces a dipole on a neighbouring molecule
Induced dipole induces further dipoles attracting one another
Temporary forces

Question 14

Strength of London forces

Answer 14

The more electrons the larger the instantaneous dipole and induced dipole
Greater the induced dipole dipole interaction
Stronger the forces

Question 15

Permanent dipole dipole

Answer 15

Act between permanent dipoles in different polar molecules

Question 16

Simple molecular substance

Answer 16

Simple molecules gorm a simple molecular lattice held by weak intermolecular forces
Low mp/bp
Non polar soluble in non polar solvents
When added to polar substance intermolecular forces in polar substance is too strong to be broken

Question 17

Hydrogen bonds

Answer 17

Hydrogen atom connected to an Electronegative atom with a lone pair of electrons
Water has relatively high bp/mp has London forces and hydrogen bonds