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A-level Chemistry > 3 - Bonding > Flashcards

3 - Bonding Flashcards

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1
Q

What are the three types of strong chemical bonds?

A

Ionic, covalent and metallic.

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2
Q

What does ionic bonding occur between?

A

Metals and non-metals

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3
Q

Explain the conductivity of ionic compounds.

A

Do not conduct electricity when solid, as no free electrons. However they are able to conduct when molten.

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4
Q

Why are ionic compounds brittle?

A

They form a lattice of alternating positive and negative ions. Therefore when stuck, ions may be moved to cause contact between like-charged ions.

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5
Q

What state are ionic compounds at room temperature? (Think NaCl)

A

Solid

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6
Q

Where does covalent bonding occur?

A

Between a pair of non-metal atoms.

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7
Q

What is a covalent bond?

A

A shared pair of electrons between two non-metal atoms.

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8
Q

Why do covalent molecules have low melting points?

A

Between the molecules there are only weak intermolecular forces. The covalent bonds are strong, however they are between atoms within the individual molecules.

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9
Q

Explain the conductivity of covalent molecules.

A

The molecules are neutral overall, meaning there are no charged particles.

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10
Q

What is a co-ordinate bond?

A

It serves as a covalent bond, but one atom donates a pair of electrons (a lone pair) and the other (that is electron deficient) gives none.

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11
Q

What are the properties of a dative covalent bond?

A

Same strength and length as ordinary covalent bonds.

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12
Q

What is a co-ordinate bond also known as?

A

A dative covalent bond.

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13
Q

What is electronegativity?

A

The ability of an atom to attract electron density in a covalent bond, towards itself.

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14
Q

What does electronegativity depend on? (3)

A

Nuclear charge

Distance between nucleus and outer shell electrons

Shielding of nuclear charge by electrons in inner shells

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15
Q

What are the trends in electronegativity across the periodic table?

A

Increase across periods

Increase up groups

So higher electronegativity in the top right

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16
Q

What is a polar bond?

A

One in which the electron density is slightly towards one of the atoms, due to a difference in electro negativity. Partial charges.

17
Q

Where does metallic bonding occur?

A

In metal elements.

18
Q

Describe metallic bonding.

A

In a metal, outer shells of atoms merge. These electrons no longer associate with particular atoms so are ‘in a sea’ of delocalised electrons, which surrounds a lattice of positive ions.

19
Q

Why are metals good conductors of both electricity and heat?

A

The delocalised electrons are able to move and also very vigorously vibrate, carrying energy.

20
Q

Why are metals ductile (can be pulled into wires) and malleable (can be beaten into a shape)?

A

After a small distortion, each ion is still in the same environment so shape is maintained.

21
Q

Why do metals have high melting and boiling points?

A

They have giant structures, and strong attraction between the metal ions and delocalised sea of electrons, making the atoms difficult to separate.

22
Q

What are the three types of intermolecular forces? (In strength order)

A

van der Waals

dipole-dipole

hydrogen bonding

23
Q

When do dipole-dipole forces form?

A

Between two molecules with permanent dipoles, they will attract.

24
Q

The size of van Det Waals increases with what?

A

The number of electrons present, so larger molecules produce stronger van der Waals

25
Q

What do hydrogen bonds form between?

A

A hydrogen atom bonded to a very electronegative atom, this makes the H strongly partially positive.

A very electronegative atom with a lone pair, which is attracted to the hydrogen in the other molecule.

Can form between H and O, N, F.

26
Q

What happens when ice freezes?

A

Hydrogen bonds form between the molecules, which increase spacing and makes it less dense than water.

27
Q

What evidence is there to show the strength of hydrogen bonds?

A

Period 2 Hydrides (group 4,5,6,7) have much higher boiling points than other periods.

28
Q

Why is there no temperature change while changing states?

A

Any energy supplied is absorbed to weaken the forces between particles.

29
Q

What are the four types of crystals?

A

Ionic crystals
Metallic crystals
Molecular crystals
Macromolecular

30
Q

Why do molecular crystals have low boiling points?

A

The intermolecular forces are weak, covalent bonds only exist inside the individual molecules.

31
Q

What is a macromolecular structure?

A

A giant structure all held together by covalent bonds, leading to a high melting temperature.

32
Q

Give an example of an ionic crystal?

A

Sodium chloride, NaCl

A-level Chemistry (34 decks)

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