Chapter 5+6

Question 1

Quantum theory’s formula for no.electrons in a certain shell.

Answer 1

n = 2n squared

Question 2

Definition of an orbital

Answer 2

A volume of space around the nucleus that can hold up to 2 electrons with opposite spins.

Question 3

What shape do s-orbitals have?

Answer 3

Spherical shape

Question 4

What shape do p-orbitals have?

Answer 4

Dumb-bell shaped. There are 3 separate p-orbitals at right angles to each other.

Question 5

Definition of ionic bonding.

Answer 5

The electrostatic attraction between cations and anions.

Question 6

What property do ions have after ionic bonding?

Answer 6

A stable electron configuration (a noble gas configuration).

Question 7

What are the properties of a giant ionic lattice?

Answer 7

1. Solid at room temp
2. High melting/boiling points as it requires a high amount of energy to overcome bonds between cations and anions.
3. Dissolve in polar solvents e.g water.
4. Conducts electricity in molten form as ions are free to move and carry electrical charge.

Question 8

What do melting/boiling points depend on in a giant ionic lattice?

Answer 8

1. Ionic charges
2. Size of ions.

• smaller ions and higher charges increase melting/boiling points.

Question 9

Definition of an element.

Answer 9

Made up of one type of atom.

Question 10

Definition of a compound

Answer 10

A substance containing two or more elements chemically bonded together.

Question 11

Definition of a molecule.

Answer 11

Two or more atoms covalently bonded together.

Question 12

Definition of a covalent bond.

Answer 12

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms. (Is the overlap of atomic orbitals each containing 1 electron).

Question 13

What directions do ionic and covalent attractions act in?

Answer 13

Ionic - all directions
Covalent - attraction is solely between shared pair of electrons in the bond and the nuclei of the bonding atoms.

Question 14

What are electrons that are not part of the covalent bond called?

Answer 14

Lone pairs.

Question 15

Definition of dative covalent bond.

Answer 15

A shared pair of electrons in which the bonded pair of electrons is from one of the bonding atoms only.

Question 16

What does the electron-pair repulsion theory state?

Answer 16

Pairs of electrons around a central atom repel each other, so move as far apart to minimise the repulsion.

Question 17

What is the molecular shape and angle for two electron pairs/densities?

Answer 17

Linear. 180•

Question 18

What is the molecular shape and angle for three electron pairs/densities?

Answer 18

Trigonal planar. 120• (still on a flat plane - not 3D)

Question 19

What is the molecular shape and angle for four electron pairs/densities?

Answer 19

Tetrahedral. 109.5• (3D)

Question 20

What is the molecular shape and angle for five electron pairs/densities?

Answer 20

Trigonal bipyramidal. (Trigonal planar with a pole in the middle)
Two bond angles - 90 and 120•.

Question 21

What is the molecular shape and angle for six electron pairs/densities?

Answer 21

Octahedral - 90•

Question 22

What is the molecular shape and angle for four electron pairs/densities but 1 lone pair.

Answer 22

Pyramidal. 109.5 - 2.5 =107•

Question 23

What is the molecular shape and angle for four electron pairs/densities but with 2 lone pairs.

Answer 23

Non-linear. 109.5 - 2.5 - 2.5 =104.5

Question 24

Why and how do lone pairs affect the repulsion of electron pairs?

Answer 24

The lone pair is slightly closer to the central atom so therefore repels more than a bonded pair.

Question 25

Definition of electronegativity.

Answer 25

A measure of the ability of an atom in a molecule to attract a pair of electrons in a covalent bond to itself.

Question 26

Definition of a non-polar bond.

Answer 26

Where the bonded electron pairs is shared equally (occurs when atoms are the same or have equal electronegativity).

Question 27

Definition of a polar bond.

Answer 27

The bonded electron pair is shared unequally (as atoms are different or have diff. electronegativity values). The separation of opposite charges is called a dipole.

Question 28

Will symmetrically opposing dipoles cancel out? E.g in CO2

Answer 28

Yes. Also true with BF3 and CCl4.
If they don’t cancel out (e.g in H2O) an overall dipole arrow is drawn.

Question 29

Definition of intermolecular forces.

Answer 29

Intermolecular forces are weak interactions between dipoles of different molecules.

Question 30

What do intermolecular forces cause in substances?

Answer 30

Their physical properties.

Question 31

How are London forces formed?

Answer 31

An uneven distribution of moving electrons causes a bulge (instantaneous dipole) which induces surrounding electrons creating an induced dipole, leading to an attraction. These are temporary.

Question 32

When do London forces increase?

Answer 32

As molecules get larger, no.electrons increases so size of induced dipoles also increases, giving stronger forces.
As these increase, more energy is needed to overcome them - so higher melting/boiling points.

Question 33

Where are permanent dipole-dipole (PDD) forces formed?

Answer 33

Formed between polar molecules. Opposite dipoles attract each other.

Question 34

What is hydrogen bonding?

Answer 34

A type of PDD force containing either N, O or F, and a hydrogen atom attached.

Question 35

Why is ice less dense than water?

Answer 35

Hydrogen bonds lock the open lattice into separate tetrahedral arrangements, but in a liquid state H bonds break and water can move in (becoming denser).

Question 36

Why does water have high surface tension?

Answer 36

Molecules on the surface experience unbalanced H bond forces pulling them in.