KA4- Bonding

Question 1

Diatomic molecules

Answer 1

2 atoms share electrons
2 atoms covalently bonded together
Both atoms have an equal ‘pull’ on the shared electrons
They have the same electronegativity
Pure covalent bond/ non-polar covalent bond

Question 2

Pure covalent bonding

Answer 2

Occurs in compounds where both atoms have the same electronegativity

Question 3

Polar covalent bonding (polar molecules)

Answer 3

Atom with slightly higher electronegativity has a slight negative charge and the other has a slight positive charge
Atom with highest electronegativity attracts electrons more strongly than the other atom
Atoms with different electronegativity value form a covalent bond
Polar moles area attracted to other polar molecules by pdp-pdp interactions or brogan bonding

Question 4

Ionic bonding

Answer 4

Atoms with a large difference in electronegativity
The attraction between the positive ions of one element and the negative ions of the other element
Doesn’t involve the sharing of electron
Occurs where electrons are transferred from one atom to another causing one atom to lose electrons (and become positively charged) and the other atom to gain electrons (and become negatively charged)
Metal+non-metal (metal has a low electronegativity value)

Question 5

The bonding continuum

Answer 5

To figure out differences in bonding
The one with the greatest difference in electronegativity would usually be the most ionic/ covalent

Question 6

Ionic bonding features

Answer 6

Conduct electricity when molten or when dissolved in water
Tend to have high melting points as a lot of energy is required to break the strong bonds that exist in the ionic lattice formed by such compounds in the solid state
Usually soluble in water
Held together in the solid state by covalent bonds

Question 7

Covalent compound properties

Answer 7

Don’t conduct electricity
Smaller molecules have lower melting points and the larger molecules have higher melting points (varied)
Held together in the solid state by ionic bonds
Some held together in the solid state by forces of attraction known as van der Waals’ forces

Question 8

Main types of van der Wals’ forces

Answer 8

London dispersion forces
Permanent dipole-permanent dipole interactions
Hydrogen bonding

Question 9

London dispersion forces

Answer 9

Between all molecules and atoms
The only force between non-polar molecules and monatomic elements
The weakest attractive forces
Caused by the uneven distribution of moving electrons

Question 10

Permanent dipole-permanent dipole interactions

Answer 10

Between polar molecules
Much stronger than London dispersion forces

Question 11

Hydrogen bonding

Answer 11

Between polar molecules where a H atom is directly bonded to an N, O or F atom
Strongest

Question 12

London dispersion forces explained

Answer 12

The side of the atom which has an excess of electrons becomes negative, causing the other side of the atom to become positive
The electrons in a neighbouring atom will shift away from an approaching negative causing a positive to appear- known as an induced dipole

Question 13

Noble gases properties

Answer 13

Held together in the solid state by London dispersion forces
As you descend the noble gases, the melting point increases as it takes more energy to overcome the London dispersion forces between the atoms because of the number of electrons increasing

Question 14

Permanent dipole-permanent dipole interactions explained

Answer 14

The permanent dipole in one … molecule is attracted to the permanent dipole in a neighbouring … molecule

Question 15

Non polar molecules

Answer 15

Held together by London dispersion forces

Question 16

Polar compounds

Answer 16

Held together by permanent dipole-permanent dipole interactions or hydrogen bonds

Question 17

Polar solvent

Answer 17

The end of the molecules have slight positive and negative charges

Question 18

Non polar/polar dissolving

Answer 18

Polar and ionic substances will not dissolve in non polar substances
Non polar compounds can dissolve in non-polar solvents but not in polar solvents

Question 19

Viscous liquids

Answer 19

Have stronger intermolecular forces between molecules
Increasing the number of hydroxyl groups in a molecule increases viscosity

Question 20

Density

Answer 20

When most liquids become solids the density of the solid is greater than that of the liquid since the particles in the solid state are packed much closer together compared to the particles in h the liquid state

Question 21

Non polar covalent bonds (non polar molecules)

Answer 21

2 atoms with the same electronegativity value
Atoms have equal attraction for electrons in the covalent bond
Non-polar molecules are attracted to other non-polar molecules by LDF