Chem Unit 1 (Bonding) Flashcards Preview

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Flashcards in Chem Unit 1 (Bonding) Deck (32)
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1
Q

Ionic Bonding

A

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.

2
Q

Properties of ionic bonding:

A

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.

3
Q

Covalent bonding

A

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

4
Q

Electronegativity

A

power of a nucleus to attract electron density

5
Q

Electronegativity depends on:

A
  • nucleur charge
  • atomic radius
  • amount fo shieling
6
Q

Order of electronegativity:

A
  • Fluorine
  • Oxygen
  • Nitrogen
  • Chlorine
7
Q

Polarity

A

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.

8
Q

Intermolecular forces: Van der Waals/ Temporary dipole-dipole

A

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

9
Q

Permanent Dipole-Dipoles

A

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

10
Q

Hydrogen Bonding

A

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

11
Q

Order of strengths for intermolecualr forces

A

Hydrogen Bonding>Permanent dipole-dipole>Van der Waals

12
Q

why is ice less dense than water?

A

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.

13
Q

Heating a solid?

A

This makes the particles vibrate (move slightly further apart)

14
Q

Turning a solid into a liquid?

A

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.

15
Q

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

A

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

16
Q

heating a liquid

A

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

17
Q

Turning a liquid into a gas?

A

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.

18
Q

Heating a gas?

A

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

19
Q

Metallic Bonding:

A

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

20
Q

Strength of metallic bonds depends on?

A

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.

21
Q

Hydrogen bonding in non-bonded molecules?

A

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.

22
Q

What are crystals?

A

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

23
Q

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

A

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

24
Q

Properties of Metallci crystals? e.g. Magnesium

A

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

25
Q

Simple molecular e.g. iodine

A

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)

26
Q

macromolecular crystals?

A

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

27
Q

Diamond properties?

A

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

28
Q

Graphite properties?

A

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.

29
Q

Dative/co-ordinate bonding

A

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

30
Q

Repulsion between electrons?

A

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

31
Q

Introduction of a lone pair decreases bond angle by…?

A

2.5 degrees

32
Q

To predict shape of molecules:

A

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.

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