Chp 2 - Electrons, Bonding, Structure

Question 1

Number of electrons in first 4 energy levels (shells)?

Answer 1

1st Shell 2
2nd Shell 8
3rd Shell 18
4th Shell 32

Question 2

Names the electron sub-shells?
+max electrons in those shells

Answer 2

S-orbital (Max= 2 electrons)
P-orbital. (Max= 6 electrons)
D- orbital (Max = 10 electrons)

Question 3

Shape of s-orbital?

Answer 3

Circle around nucleus
(See notes)

Question 4

Shape of p-orbital?

Answer 4

Figure of 8
(Dumbbell around nucleus across three planes)
See notes

Question 5

Def of orbital?

Answer 5

an orbital is an area of space about the nucleus that can hold a maximum of two electrons with opposite spins (high likelihood of finding an electron)

Question 6

sub-shell notation of oxygen?

Answer 6

1s^2 2s^2 2p^4

Question 7

Filling orbital?

Answer 7

Fill orbitals singularly before pairing up

Question 8

Energy levels?

Question 9

How do electrons begin to fill the p orbitals?

Answer 9

They fill singularly before pairing up in the orbitals

Question 10

Order of filling

Question 11

Ions

Answer 11

an atom with more or less electrons than protons and therefore has a charge – either positive or negative

Question 12

Clear card

Question 13

Def of ionic bonding

Answer 13

Electrostatic attraction between positive and negative ions.

Question 14

Structure of ionic compounds
(+ why)

Answer 14

Giant ionic crystal lattice structure

(Resulting from oppositely charged ions strongly attracted in all directions)

Question 15

Physical Properties of ionic compounds ?

Answer 15

High melting point
- large amounts of energy needed to overcome strong electrostatic attraction

Brittle
- dislocation leads to layers moving and similar ions being adjacent causing repulsion to split crystal

Water soluble
- polar solvent stabilises and separates ions

Electrical conductivity
- in L/AQ form ions are mobile and able to conduct
As solid = insulator

Question 16

Def of covalent Bond?

Answer 16

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

Question 17

{def of average bond empathy}

Answer 17

A measure of the strength of a covalent bond

(the stronger the bond the higher the value)

Question 18

Structures of covalent compounds?

Answer 18

Simple molecular
Giant covalent

(Polymers)

Question 19

Describe dative covalent (Co-ordinate) bonds

Answer 19

A covalent bond formed where both electrons come from the same species

Drawn with -> rather than – in display formula

Question 20

Draw diagram to show formation of co-ordinate bond

BF3 + F- —> BF4-

Answer 20

Lone pair of electrons donated from F- to B in BF3
(See notes for diagram)

Question 21

Types of chemical bonds
(Strong bonds)

Answer 21

1. Ionic
2. Covalent
3. Dative ( coordinate)
4. Metallic

Question 22

Types of physical bonds
(Weak bonds)

Answer 22

1. Induced dipole-dipole interactions (London forces)
2. permanent dipole-dipole interactions
3. hydrogen bonds

Question 23

Shape and bond angles of 2 bonds
(Species without lone pairs)

Answer 23

Shape- linear
Bond angle- 180 o

Eg. BeCl2

Question 24

Shape and bond angles of 3 bonds
(Species without lone pairs)

Answer 24

Shape- trigonal planar
Bond angles- 120 o

Eg. BF3

Question 25

Shape and bond angles of 4 bonds
(Species without lone pairs)

Answer 25

Shape- tetrahedral
Bond angles- 109.5 o

Eg. CH4

Question 26

Shape and bond angles of 5 bonds
(Species without lone pairs)

Answer 26

Shape- trigonal bipyramidal
Bond angles- 120 & 90 o

Eg. PF5

Question 27

Shape and bond angles of 6 bonds
(Species without lone pairs)

Answer 27

Shape- octahedral
Bond angles- 90 o

Eg. SF6

Question 28

Effect of lone pairs on bond angle?
[+why]

Answer 28

Each lone pair reduces the bond angle by 2.5 o
This is because they have a greater repulsion power

Question 29

Describe shape of water molecule?

Answer 29

Shape= non-linear
Bond angles= 104.5
As has 2 bonded pairs and 2 lone pairs of electrons

Question 30

Why might shapes be non-linear ?

Answer 30

Electron pair repulsion tells us the lone pairs have a higher repulsion force therefore decrease the bond angle by 2.5o

Question 31

Def of electronegativity?

Answer 31

Electronegativity is the ability of an atom to attract the bonding electrons in a covalent bond

Question 32

Electronegativity changes across the periodic table?

Answer 32

(Pauling value)
Electronegativity increases up the groups and across the periods towards fluorine

Question 33

When is polar bonds formed (permanent dipole)?

Answer 33

When molecules containing covalently-bonded atoms with different electronegativities.

Question 34

When is a polar molecule (overall permanent dipole) formed?

Answer 34

A polar molecule requires polar bonds with dipoles that do not cancel due to their direction.
(Not symmetrical)

Question 35

When do hydrogen bonds form?

Answer 35

As intermolecular bonding between molecules containing N,O,F and the H atom of -NH, -OH, -HF

Question 36

Why are water molecules properties unusual?

Answer 36

Ice is less dense than water-

relatively high melting and boiling point-

Question 37

describe how London forces arise
(3 marks)

Answer 37

1) uneven distribution of electrons
2) creates instantaneous dipole
3) induces dipoles of neighbouring molecules