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A Level Chemistry > Structure And Bonding > Flashcards

Structure And Bonding Flashcards

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1
Q

What is an ionic bond?

A

The electrostatic attraction between oppositely charges ions

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2
Q

Ionic is a —— structure

A

Giant

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3
Q

Why do ionic compounds have high melting and boiling points?

A

Lots of energy needed to break strong ionic bonds, which increases with attraction between ions (increasing charger, decreasing radius)

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4
Q

Do ionic compounds conduct electricity and explain ?

A

Only in a molten or aqueous state ions are free to move and carry charge - fixed position in lattice in solid state.

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5
Q

What is a metallic bond?

A

The electrostatic attraction between positively charged ions and it’s negatively charged delocalised sea of electrons

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6
Q

Metallic compounds are of —— structure

A

Giant

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7
Q

Explain why the melting and boiling point of metallic compounds are high?

A

Strong forces of attraction are hard to break and increases with more protons because higher charge on ion so stronger attraction to the sea or delocalised electrons

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8
Q

Explain why metals conduct electricity?

A

The delocalised electrons are free to move and carry charge.

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9
Q

What is a covalent bond?

A

The mutual electrostatic attraction between a shared pair of electrons and positively charged nuclei.

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10
Q

Two types of covalent structures

A

Giant

Simple molecular

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11
Q

Melting points of giant covalent lattices are extremely high (>1000°C) - why?

A

Many covalent bonds to break and covalent bonds require a high amounts of thermal energy.

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12
Q

The longer the covalent bond is the

A

Weaker it is

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13
Q

Why is graphite the only giant covalent structure that conducts electricity?

A

Delocalised electrons between layers are free to move (but not between layers)

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14
Q

Diamond

A

Each carbon atom forms four sigma bonds to four other carbon atoms (109.5°)

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15
Q

Why can graphite be used as a lubricant?

A

Solid lubricant because layers. Slide easily over one another because of its ability to absorb gases on the surface of carbon atoms.

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16
Q

Graphite

A

One atom forms three sigma bonds and the fourth electron of each atom is in a p orbital - because the atoms are close the p orbitals overlap to produce a cloud of delocalised electrons

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17
Q

Graphene

A

One atom thick

One atom forms three sigma bonds

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18
Q

Simple covalent bonds have low melting points

A

Weak intermolecular forces between molecules that can easily be broken

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19
Q

Sigma bond is

A

End on end overlap of s orbitals (two circles) or the end on end overlap of two p orbitals (infinity sign)

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20
Q

Pi bond

A

Sideways overlap of two p orbitals (figure of eight style)

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21
Q

A pi bond can only exist when

A

A sigma bond already exists so only found in double or triple bonds

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22
Q

The trip le bond in a nitrogen molecule is made up of

A

One sigma bond and two pi bonds

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23
Q

Atomic Emission Spectra

A

Lines correspond energy of each shell - shells are of specific energy

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24
Q

Dative covalent bonding is when

A

one atom provides both electrons in a covalent bond

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25
Q

Two elements that defy octet rule

A

Boron (six)

Sulfur (12)

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26
Q

Ionic radi trend

A

The radius will decrease with increasing positive charge

27
Q

Isoelectronic ions

A

Ions with the same number of electrons

28
Q

Two types of evidence that ions exist

A

Electrolysis

And that ions conduct electricity when molten or aqueous

29
Q

Passing an electric current through aqueous copper (II) chromate

A

Cu (II) is blue and CrO42- is yellow
The Cu2+ ions move toward the negative electrode and that area turns blue whereas the CrO42- moves toward the positive electrode and turns the area around there yellow the area in the middle becomes green

30
Q

Explanation for brittleness of ionic compounds

A

When stress is applied the layers of ions can slide over one another - the ions of the same charge are now side by side and repel one another and the crystals break apart

31
Q

Basic explanation for ions solubility in water is

A

Both +ve and -ve are attracted to water molecules due to the polarity it possesses

32
Q

Linear shaped molecule:
Number of electrons
Bond angles
Examples

A

2
180°
BeCl2
CO2

33
Q

Trigonal Planar:
Number of electrons
Bond angles
Examples

A

3
120°
BF3

34
Q

Tetrahedral:
Number of electrons
Bond angles
Examples

A

4
109.5°
CH4

35
Q

Trigonal Bipyramidal:
Number of electrons
Bond angles
Examples

A

5
120° and 90°
PCl5

36
Q

Octahedral:
Number of electrons
Bond angles
Examples

A

6
90° and 180°
SF6

37
Q

If there are lone pairs the angle between molecules decreases by —— because ——

A

2.5°

Lone pairs repel more than bonded pairs

38
Q

Pyramidal shape molecule

A

3 bonded pairs
1 lone pair
Based on tetrahedral 107°

39
Q

Non - linear/v - shaped/bent

A

2 bonded pairs
2 lone pairs
104.5°

40
Q

How to answer questions on shapes of molecules

A

Electron pairs repel. Lone pairs repel more than bonded pairs. There are —— lone pairs and —— bonded pairs which push apart as far as possible to ——°

41
Q

Double repel — —————— as single bonds.

A

The same ankh for

42
Q

Mathematical trick to figure out shape of molecule (does not work for double/triple bonds)

A

Group number of central atom:
Add e- if negative; remove if positive charge:
Add e- for each thing bonded:
Add above and divide by two to get total number of pairs then split into bonded and lone.

43
Q

Electronegativity

A

The ability of an atom to attract the bonding electrons in a covalent bond.

44
Q

Fluorine is the most electronegative atom because

A

only needs on electron has minimal shielding more nuclear charge so decreased attraction on bonding electrons hence a smaller atomic radius.

45
Q

What is a polar bond

A

Covalent bond with a difference in electronegativity

46
Q

What is a polar molecule

A

Polar bonds are not cancelling as the molecule is asymmetrical

47
Q

General rule on electronegativity

A

If the molecule is a textbook shape with the same type of atoms around the outside it is non polar because it is symmetrical hence the dipoles cancel

48
Q

Intermolecular forces are

A

Forces of attraction between molecules

49
Q

What break when water is melted?

A

Intermolecular forces

50
Q

Name the three types of intermolecular forces:

A

London forces
Permanent dipole-dipole
Hydrogen bonds

51
Q

London forces/instantaneous- induced dipole are found in all simple covalent structures. What are they?

A

Temporary uneven distribution of electrons causes an instantaneous dipole
This induces a dipole on neighbouring molecules and the net difference causes an attraction

52
Q

London forces get stronger with

A

Number of electrons (chlorine,bromine,iodine)

53
Q

Branched organic molecules have —— London forces because

Hence bp becomes

A

Weaker
Less surface contact
Do not pack well

Lower bp due to weaker intermolecular forces

54
Q

A permanent dipole - dipole is

And symbols

A

the attraction between polar molecules

Use small delta with charge to show on diagram

55
Q

Hydrogen Bonding

A

Occurs when hydrogen is directly bonded to nitrogen, oxygen or fluorine
Strongest type of intermolecular force
Label with delta and charge
H bond must touch lone pair (lines between them)
180° around H
Must label the hydrogen bond

56
Q

Electron pair repulsion theory/ valence shelll electron pair repulsion theory (VSEPR)

A

Shape of molecule/ion is cause by repulsion between the pairs of electron that surround the central atom
The electrons pairs arrange themselves around the central atom so that the repulsion between them is at a minimum
Lone-lone>lone-bonded>bonded-bonded>
(Repulsion)

57
Q

Name the anomalous properties of water

A

Ice is less dense than water

Water has a relatively high melting/boiling point

58
Q

Explanation for why ice is less dense than water

A

Hydrogen bonds are longer than covalent bonds so when they form they push the molecules further apart hence open lattice structure

59
Q

Explain why water had a relatively high melting/boiling point

A

Hydrogen bonds are relatively strong for intermolecular forces so require more energy to break

60
Q

Boiling temperature of hydrogen halides trend and explain

Also state “abnormality to trend”

A

Steady increase from HCl to HI is because of increasing the number of electrons per molecule hence increasing strength of London forces
HF is the highest because it has hydrogen bonding

61
Q

Are alcohols soluble and explain why/why not

A

They are because they can form hydrogen bonds to water molecules

62
Q

Some ionic compounds dissolve in water because of hydration

What is hydration

A

Ions of both charges are attracted to either the polarity of water molecules for example Na+ is attracted to the delta minus of oxygen

63
Q

“Like dissolves like”

A

Things that are non-polar/not hydrogen bonded willl not dissolve easily in water.

A Level Chemistry (8 decks)

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