Topic 2-Bonding

Question 1

What is metallic bonding and describe features of metals?

Answer 1

Electrostatic attraction between positive ions and a sea of delocalised electrons.
Metals are malleable and ductile

Question 2

What does the strength of metallic bonding depend on and the effect on melting and boiling point?

Answer 2

Metallic bonds depend upon the amount of protons
The more protons the stronger the metallic bond as greater nuclear charge pulls in valence electrons
This increases boiling and melting point as more energy required to overcome metallic bonds

Question 3

What is Ionic bonding and explain some properties?

Answer 3

Bond between positive and negative ions held together by electrostatic forces of attraction
Involves transfer of electrons

High Melting point
Soluble in water as they are charged
Does not conduct electricity in solids
Cannot be shaped
Brittle-As repulsion between same charged ions are strong

Question 4

What is covalent bonding?

Answer 4

Electrostatic attraction between positive nucleus and negative electrons
It forms between 2 non metals
Involves sharing of electrons

Question 5

What evidence is there for the existence of ions?

Answer 5

Migration of ions on wet filter paper-electrolysis of copper chromate
Electron Density Maps

Question 6

Why does Ionic bonding have high melting and boiling points?

Answer 6

Strong electrostatic forces of attraction between oppositely charged ions so more energy is required to break forces

Question 7

Why can Ionic compounds conduct electricity in solution but not in solids?

Answer 7

In solutions,ions are free to move and carry charge so it can conduct electricity
In solids,ions cannot move

Question 8

Explain the properties of Diamonds?

Answer 8

High Melting Point- as it has strong covalent binds so lots of energy is required to overcome these bonds

High strength as each carbon is joined to 4 others so has a coordination no. of 4,strong delocalised electrons

Cannot conduct electricity

Question 9

Explain the bonding,structure and properties of graphite?

Answer 9

High Melting Point-Has lots of strong covalent bonds so lots of energy required to break bonds
Each Carbon bonded to 3 others

Strength- Low strength as it has weak intermolecular forces of attraction so layers can slide over each other

Can conduct electricity as it has delocalised electrons

Question 10

How does Ionic charges and Ionic Radii affect Ionic bonding?

Answer 10

The Greater the charge of the ion,the stronger the Ionic bond and so a higher melting and boiling point

The smaller the Ionic radii the greater the Ionic bonding as electrostatic attraction is greater when Ionic radii is small so it is stronger and has a higher melting and boiling point

Question 11

Explain how Ionic radius changes down the group?

Answer 11

Ionic Radius increases down the group as atomic number is greater so there is more electron shell

Question 12

What is a dative covalent bond?

Answer 12

This is where one atom donates both electrons to a bond for example carbon monoxide
Contributes to donate both electrons to form a covalent bond

Question 13

Explain the properties of giant covalent bonds?

Answer 13

Strong covalent bonds and strong electrostatic forces of attraction allow:
Very High Melting points
Extremely hard-strong bonds in the regular lattice,so atoms cannot slide past each other
Good thermal conductors
Insoluble-As atoms are more attracted to neighbours than to solvent molecules
Cannot conduct electricity

Question 14

Explain the angle size difference between lone pairs and electron pairs?
Explain the effect of electron repulsion on angle size?

Answer 14

As you know,pairs of electrons will always repel so stronger repulsion means greater angle difference
Lone pairs have stronger repulsion so they have greater angle size

Question 15

What is the Octet rule and what elements are exemptions and why?

Answer 15

Tendency of electrons to have 8 electrons in the outer shell
Elements in the 3rd row or below don’t need to follow the Octet rule as they can have more electrons as they can promote some electrons in a 3d subshell
They can have upto 18

Question 16

What are hypervalent compounds?

Answer 16

Compounds that do not follow the Octet rule and can have more than 8 electrons in a subshell

Question 17

What is a sigma bond?

Answer 17

Is the overlap of a covalent bond which passes the internucleaur axis
Single bonds are sigma

Question 18

What is a pi bond?

Answer 18

Pi bonds are a bond between 2 covalent bonds where it passes the internucleur axis
Double bonds have 1 sigma and 1 pi bond
Triple bonds have 1 sigma and 2 pi bonds

Question 19

What is a molecule?

Answer 19

An uncharged group of 2 or more atoms stuck together

Question 20

What is a double bond?

Answer 20

Its where 2 pairs of electrons are shared between 2 elements

Question 21

Explain how the length of a covalent bond is dependant on the relative atomic mass?

Answer 21

Greater relative atomic mass means that there is more electrons and greater nuclei distance so that means the length of the covalent bond is greater.

Question 22

Explain how the proton number affects the length of a covalent bond?

Answer 22

The Greater the proton number,the greater the attraction between positive nuclei and outer electrons so this means atomic radius is smaller so length of covalent bond is smaller

Question 23

How are dative bonds represented?

Answer 23

They are represented by 2 dots or 2 crosses or as an arrow

Question 24

What is needed for a dative bond to form?

Answer 24

An element/atom needs a lone pair of electrons to form a full outer shell
It requires an acceptor and a donor

Question 25

What is the Valence Shell Electron pair repulsion theory and its purpose?

Answer 25

This is a theory used to predict the geometry of molecules based on minimising electron repulsion

Question 26

How is the shape of a molecule determined?

Answer 26

It is determined by the electron pairs surrounding the central atom
This is based on the fact that pairs of electrons repel other pairs of electrons
This means electron pairs move as far as possible creating bigger bond angles

Question 27

What angle does lone pairs decrease bond angle by and why?

Answer 27

Each lone pair decreases bond angle by 2.5 degrees and this is because they create repulsion
A lone pair also counts as a region

Question 28

What is the bond angle for tetrahedron?

Answer 28

It’s 109.5

Question 29

Describe the geometry of water,shape and bond angles

Answer 29

Water is a tetrahedron with a bent shape as it has 4 electron density regions(2 bonding pairs and 2 lone pairs)
It has a bond angle of 104.5 and 109.5-2.5-2.5 is 104.5

Question 30

Explain variations in melting temperature across period 3 in terms of structure and bonding?

Answer 30

Na,Mg,Al have metallic bonding,number of protons increase,radius decreases so metallic bond strength increases
Si is a giant covalent molecule so lots of energy required to break covalent bonds
Phosphorus is a simple molecular so it has low melting pointe as it has weak intermolecular forces

Question 31

What is electronegativity?

Answer 31

The power/ability of an element to attract the shared pair of electrons in a covalent bond

Question 32

Explain how electronegativity changes down a group?

Answer 32

Electronegativity decreases down the group as shielding increases which decreases the effective nucleur charge so the element is less likely to attract electrons as positive nuclear charge is lowered by shielding

Question 33

Explain how electronegativity changes across a period?

Answer 33

Across a period,electronegativity increases as proton no increases so effective nucleur charge increases as atomic radius gets smaller

Question 34

What is the Pauling Electronegativity of non polar,polar and Ionic compounds?

Answer 34

Non polar-0 to 0.5
Polar-0.5 to 1.7
Ionic-Greater than 2 and smaller than 4(4 is max and fluorine has EN of 4 )

Question 35

What does electronegativity show in a compound?

Answer 35

In a compound such as HCL the element with a greater EN will have a greater share of the shared electron pair so its slightly more negative whereas the other is positive

Cl has a greater EN so its delta negative

Question 36

Explain how lone pairs affect electronegativity?

Answer 36

Molecules with one or more lone pairs on the central atom are always polar as it breaks the symmetry

Question 37

What are intermolecular forces and the 3 examples?

Answer 37

Intermolecular forces are forces between molecules and are weaker than Ionic and covalent
London forces(instantaneous dipole dipole bonds)
Permanent dipole dipole forces
Hydrogen bonding(strongest type)

Question 38

What are London forces?

Answer 38

They are fluctuations in electrical distribution within atoms and molecules
They can induce another temporary dipoles forming weak london forces
They are instantaneous dipole forces

Question 39

Explain how to increase strength of london forces?

Answer 39

Larger molecules(such as down the group) has larger electron clouds so stronger london forces
Increase SA increases strength of london forces
Greater electrons increase the strength

Question 40

What are permanent dipole dipole forces and what compounds have these?

Answer 40

Polar compounds have permanent dipole dipole forces as they have some sort of electronegativity

Question 41

Explain the strength of forces/bonding of london,hydrogen,dipole,covalent

Answer 41

London-weakest
Dipole dipole
Hydrogen-very strong
Covalent-strongest

Question 42

What is hydrogen bonding and what elements can it occur with?

Answer 42

Hydrogen bonding is the electrostatic attraction between negative oxygen and positive hydrogen
They only occur in OH,FH,NH bonds

Question 43

Why can hydrogen bonding only occur with elements:fluorine,oxygen and nitrogen?

Answer 43

These are the most electronegative elements so they draw the binding electrons away
Lone pairs make the bond polarised