Chem Unit 1 (Bonding)

Question 1

Ionic Bonding

Answer 1

non metals and metals
involves the transfer of electrons from the metal ion (loses electrons to form positively charged ions- oxidised) to the non-metal ion that gains electrons to form negatively charged ions (its reduced)
- results in them both having full outer shells
The positive and negative ions are arranged in a regular arrangement in a lattice shape.

Question 2

Properties of ionic bonding:

Answer 2

high m.p and b.p because it takes a lot of energy to overcome the strong electrostatic attraction between the positively and negatively charged ions.
Can conduct electricity when molten because liquids have delocalised electrons that carry the charge
Brittle- blow it, it shatters because the blowing ruins the alternate arrangement of positive and negative and charges of the same repel each other.

Question 3

Covalent bonding

Answer 3

bonding between non-metals and other non-metals
sharing electrons in a covalent bond
double bonded- sharing 2 pairs
triple bonded- sharing 3 pairs
Strong electrostatic attraction between positively charged nuclei and the negative electrons

Question 4

Electronegativity

Answer 4

power of a nucleus to attract electron density

Question 5

Electronegativity depends on:

Answer 5

• nucleur charge
• atomic radius
• amount fo shieling

Question 6

Order of electronegativity:

Answer 6

• Fluorine
• Oxygen
• Nitrogen
• Chlorine

Question 7

Polarity

Answer 7

When two atoms in a covalent bond have similar electronegativity values, their electron density is symmetrical so they are non-polar
When one molecule is more electronegative than the other the one which draws more electrons towards it is $- (electron density is uneven) and the other one turns $+ so it is polar
The bigger the difference in electronegatvity the more polar it is.

Question 8

Intermolecular forces: Van der Waals/ Temporary dipole-dipole

Answer 8

Even with non-polar bonds, electrons are constantly moving around. at one moment one atoms is going to have more electrons drawn towards it making it $- inducing a temporary dipole in a neighbouring molecule making the side close to it $+.
The bigger the molecule the more Van der Waals

Question 9

Permanent Dipole-Dipoles

Answer 9

When there is a signficant differnce between electronegativity the dpole-dipole will be permanent- there will be an overall attraction.

Question 10

Hydrogen Bonding

Answer 10

Hydrogen is bonded to O, N or F
The polar bond leaves the hydrogen nuclues exposed as it only has one electron (nucleus is empty)
Lone pair of electrons on the O, N or F is attracted to the exposed positive nuclei of the hydrogen

Question 11

Order of strengths for intermolecualr forces

Answer 11

Hydrogen Bonding>Permanent dipole-dipole>Van der Waals

Question 12

why is ice less dense than water?

Answer 12

hydrogen bonds move about in water, continually making and breaking bonds. When temp drops below 4 degress they can make but can’t break bonds as easily (less free)
Holds them in a semi-crystallien form, they fi into theur structure- less densely packed.

Question 13

Heating a solid?

Answer 13

This makes the particles vibrate (move slightly further apart)

Question 14

Turning a solid into a liquid?

Answer 14

Have to supply enough heat energy to force the particles to move independantly of each other. The energy needed to weaken the forces is called enthalpy change of fusion.

Question 15

Why doesn’t the temperature change when heating solid>liquid or liquid>gas?

Answer 15

Because the heat energy is absorbed/used up to weaken the bonds

Question 16

heating a liquid

Answer 16

Heating a liquid means it expands because the particles move further apart

Question 17

Turning a liquid into a gas?

Answer 17

Th energy is needed to break ALL the intermolecular forces so the particles can move far away from each other. The energy needed to break the bonds is called the enthalpy change if vaporisaion.

Question 18

Heating a gas?

Answer 18

When you heat a gas, it expands becuase the aprticles have gained knetic energy so can move far apart.

Question 19

Metallic Bonding:

Answer 19

Metals are malleable becuase once you initially distort them they are in the same environment so they maintain their previosu shape.
Strong electrostatic attraction between positively charged ions and sea of delocalised electrons.
Conduct electricity because of the delocalsied electrons carrying the current and the energy spread out between the vigorous vibrations of the particles

Question 20

Strength of metallic bonds depends on?

Answer 20

Charge of ion: Greater charge means more delocalised electrons so strogner eletrostatic attraction
Size of ion: smaller ions means the electrons are closer to the nuclues so stronger electrostaic attraction.

Question 21

Hydrogen bonding in non-bonded molecules?

Answer 21

Not all molecules in liquid water have hydrogen bonds at any one time. Some non-bonded molecuels are close to what the hydogen-bionding positin allows. When water is heated the particles move further apart, offstting the attraction betweent he hydorgen bonds
The water becomes less desnse as the volume increaees.

Question 22

What are crystals?

Answer 22

Solids with a regular arrangenment of particles, held together by forces of attracion
Could be bonding or intermolecualr forces

Question 23

What are the properties of ionic crystals? e.g. NaCl

Answer 23

Arranged in a lattice with positive and negatie ions next to each other./ strong electrostauc attraction so huigh m.p and b.p/ delocalised electrons when molten/brittle

Question 24

Properties of Metallci crystals? e.g. Magnesium

Answer 24

lattice of positively charged ions embedded in a sea of delocalsied electrons
High m.p and b.p due to strogn electrostatic attraction
Conduct electrcity- free electrons
Hardness depends

Question 25

Simple molecular e.g. iodine

Answer 25

Low m.p and b.p
Strong covalent bonds within molecules but weakVan der Waals forces of attraction between molecules - soft and breaks easily (not much energy to overcome)

Question 26

macromolecular crystals?

Answer 26

Have strong, covaklent bonds all the way through the giant strucurre (between molecules as wella s within them)

Question 27

Diamond properties?

Answer 27

Each carbon atom is bonded to 4 others
Strong covalent bonds so requires a lot fo energy to break (high m.p and b.p)
Doesn’t conduct electricity as there are no spare electrons

Question 28

Graphite properties?

Answer 28

Each carbon atom is bonded to 3 other carbon atoms leaving electrons (from the spare carbon atom) spare to carry a current.
High m.p and b.p to overcome covalent bonds
Because of the arrangemetn of carbon atoms, there are hexagonal layers that are only held togetrher by weak Van der Waals so can slide over each other easily.

Question 29

Dative/co-ordinate bonding

Answer 29

When two electrons are being shared in a covalent bond but one of the molecules donates both the electrons instead of one from each. The atom/ion that accepts the pair of electrons is electron-deficient.
The 2 electrons from one molecule is represented by an arrow

Question 30

Repulsion between electrons?

Answer 30

Electrons arrange themselves to be as far away from each other as they can.
Strength: Lone/Lone
Bonding/Lone
Bonding/Bonding

Question 31

Introduction of a lone pair decreases bond angle by…?

Answer 31

2.5 degrees

Question 32

To predict shape of molecules:

Answer 32

1) add together number f bonding pairs to group number of other molecule to find out how many total electrons.
2) Times the bonding number it gives you by 2 to see how many bonding pairs
3) Take away that number from total number of electrons and see if there are any left- i.e. sny lone electrons - divide by 2 to get lone pairs
4) Determine shape of molecule
5) Look for any lone pairs to see how it would affect your drawing of the space between the lone pairs.