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

Def of ionic bonding

Answer 12

Electrostatic attraction between positive and negative ions.

Question 13

Structure of ionic compounds
(+ why)

Answer 13

Giant ionic crystal lattice structure

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

Question 14

Physical Properties of ionic compounds ?

Answer 14

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 15

Def of covalent Bond?

Answer 15

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

Question 16

{def of average bond empathy}

Answer 16

A measure of the strength of a covalent bond

(the stronger the bond the higher the value)

Question 17

Structures of covalent compounds?

Answer 17

Simple molecular
Giant covalent

(Polymers)

Question 18

Describe dative covalent (Co-ordinate) bonds

Answer 18

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

Drawn with -> rather than – in display formula

Question 19

Draw diagram to show formation of co-ordinate bond

BF3 + F- —> BF4-

Answer 19

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

Question 20

Types of chemical bonds
(Strong bonds)

Answer 20

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

Question 21

Types of physical bonds
(Weak bonds)

Answer 21

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

Question 22

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

Answer 22

Shape- linear
Bond angle- 180 o

Eg. BeCl2

Question 23

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

Answer 23

Shape- trigonal planar
Bond angles- 120 o

Eg. BF3

Question 24

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

Answer 24

Shape- tetrahedral
Bond angles- 109.5 o

Eg. CH4

Question 25

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

Answer 25

Shape- trigonal bipyramidal Bond angles- 120 & 90 o Eg. PF5

Question 26

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

Answer 26

Shape- octahedral Bond angles- 90 o Eg. SF6

Question 27

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

Answer 27

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

Question 28

Describe shape of water molecule?

Answer 28

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

Question 29

Why might shapes be non-linear ?

Answer 29

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

Question 30

Def of electronegativity?

Answer 30

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

Question 31

Electronegativity changes across the periodic table?

Answer 31

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

Question 32

When is polar bonds formed (permanent dipole)?

Answer 32

When molecules containing covalently-bonded atoms with different electronegativities.

Question 33

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

Answer 33

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

Question 34

When do hydrogen bonds form?

Answer 34

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

Question 35

Why are water molecules properties unusual?

Answer 35

**Ice is less dense than water**- **relatively high melting and boiling point**-

Question 36

*describe how London forces arise* (3 marks)

Answer 36

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