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A Level Chemistry > Structure And Bonding > Flashcards

Structure And Bonding Flashcards

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
Two elements that defy octet rule
Boron (six) | Sulfur (12)
26
Ionic radi trend
The radius will decrease with increasing positive charge
27
Isoelectronic ions
Ions with the same number of electrons
28
Two types of evidence that ions exist
Electrolysis | And that ions conduct electricity when molten or aqueous
29
Passing an electric current through aqueous copper (II) chromate
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
Explanation for brittleness of ionic compounds
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
Basic explanation for ions solubility in water is
Both +ve and -ve are attracted to water molecules due to the polarity it possesses
32
Linear shaped molecule: Number of electrons Bond angles Examples
2 180° BeCl2 CO2
33
Trigonal Planar: Number of electrons Bond angles Examples
3 120° BF3
34
Tetrahedral: Number of electrons Bond angles Examples
4 109.5° CH4
35
Trigonal Bipyramidal: Number of electrons Bond angles Examples
5 120° and 90° PCl5
36
Octahedral: Number of electrons Bond angles Examples
6 90° and 180° SF6
37
If there are lone pairs the angle between molecules decreases by —— because ——
2.5° | Lone pairs repel more than bonded pairs
38
Pyramidal shape molecule
3 bonded pairs 1 lone pair Based on tetrahedral 107°
39
Non - linear/v - shaped/bent
2 bonded pairs 2 lone pairs 104.5°
40
How to answer questions on shapes of molecules
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
Double repel — —————— as single bonds.
The same ankh for
42
Mathematical trick to figure out shape of molecule (does not work for double/triple bonds)
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
Electronegativity
The ability of an atom to attract the bonding electrons in a covalent bond.
44
Fluorine is the most electronegative atom because
only needs on electron has minimal shielding more nuclear charge so decreased attraction on bonding electrons hence a smaller atomic radius.
45
What is a polar bond
Covalent bond with a difference in electronegativity
46
What is a polar molecule
Polar bonds are not cancelling as the molecule is asymmetrical
47
General rule on electronegativity
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
Intermolecular forces are
Forces of attraction between molecules
49
What break when water is melted?
Intermolecular forces
50
Name the three types of intermolecular forces:
London forces Permanent dipole-dipole Hydrogen bonds
51
London forces/instantaneous- induced dipole are found in all simple covalent structures. What are they?
Temporary uneven distribution of electrons causes an instantaneous dipole This induces a dipole on neighbouring molecules and the net difference causes an attraction
52
London forces get stronger with
Number of electrons (chlorine,bromine,iodine)
53
Branched organic molecules have —— London forces because Hence bp becomes
Weaker Less surface contact Do not pack well Lower bp due to weaker intermolecular forces
54
A permanent dipole - dipole is | And symbols
the attraction between polar molecules | Use small delta with charge to show on diagram
55
Hydrogen Bonding
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
Electron pair repulsion theory/ valence shelll electron pair repulsion theory (VSEPR)
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
Name the anomalous properties of water
Ice is less dense than water | Water has a relatively high melting/boiling point
58
Explanation for why ice is less dense than water
Hydrogen bonds are longer than covalent bonds so when they form they push the molecules further apart hence open lattice structure
59
Explain why water had a relatively high melting/boiling point
Hydrogen bonds are relatively strong for intermolecular forces so require more energy to break
60
Boiling temperature of hydrogen halides trend and explain | Also state “abnormality to trend”
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
Are alcohols soluble and explain why/why not
They are because they can form hydrogen bonds to water molecules
62
Some ionic compounds dissolve in water because of hydration | What is hydration
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
“Like dissolves like”
Things that are non-polar/not hydrogen bonded willl not dissolve easily in water.

A Level Chemistry (8 decks)

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