Bonding

Question 1

What is electronegativity?

Answer 1

The power of an atom to attract the pair of electrons in a covalent bond.

Question 2

Why does electronegativity decrease down a group?

Answer 2

Further from nucleus, harder for nucleus to attract another electron.

Question 3

Why does electronegativity increase across a period?

Answer 3

More protons decrease the atomic radius making it easier to gain an electron.

Question 4

What is a polar bond?

Answer 4

A covalent bond in which electrons are shared unequally (difference in electronegativity).

Question 5

What is ionic bonding?

Answer 5

Strong electrostatic forces of attraction between oppositely charged ions held in a lattice.

Question 6

What are the melting and boiling points of ionic compounds like?

Answer 6

Ionic compounds have high melting points and boiling points because of their giant ionic lattice and the strong attraction between bonds.

Question 7

Do ionic bonds conduct electricity?

Answer 7

Not in a solid state because ions are not free to move. In liquid or solution they can because ions are free to move.

Question 8

What increases the strength of ionic bonding?

Answer 8

Greater charge and smaller ionic radius.

Question 9

What is metallic bonding?

Answer 9

Strong electrostatic attraction between cations and the sea of delocalised electrons.

Question 10

How many cations should you draw in an exam for metallic bonding diagrams?

Answer 10

At least 6 and have delocalised electrons proportional to that.

Question 11

What affects the strength of a metallic bond?

Answer 11

Ionic charge (higher=stronger), number of delocalised electrons (more=stronger), ionic radius (smaller=stronger).

Question 12

What are the melting and boiling points of metals like?

Answer 12

High because of the giant metallic lattice and the strong attraction between cations and delocalised electrons.

Question 13

Do metals conduct electricity?

Answer 13

Yes, the free electrons are able to carry a charge.

Question 14

Why are metals malleable?

Answer 14

The layers of atoms in a metal can slide over each other and the attraction between electrons and cations keeps the compound together.

Question 15

What is a covalent bond?

Answer 15

Sharing of electrons between atoms.

Question 16

What does expanding the octet mean?

Answer 16

Having more than 8 electrons in their outer shell.

Question 17

What is needed for a co-ordinate bond to occur?

Answer 17

Atom donating must have a lone pair, atom receiving must have a free orbital.

Question 18

What is a co-ordinate bond represented by?

Answer 18

An arrow.

Question 19

How do you find a molecule’s number of lone pairs?

Answer 19

Identify the group number of the central atom which shows how many outer electrons it has. If it’s an ion add or subtract the charge. Count the number of single bonds formed by the central atom and add this to the total from step 2. Divide this by two which shows how many electron pairs there are. Minus the number of bonds from this number. That will show the lone pairs.

Question 20

What is the electron pair repulsion theory?

Answer 20

LP-LP>BP-LP>BP-BP. Molecules will form the shape that has the least repulsion.

Question 21

What do angles decrease by for each LP?

Answer 21

2.5°.

Question 22

What are the three types of intermolecular forces?

Answer 22

Van der Waals Forces, Dipole-dipole forces and hydrogen bonding.

Question 23

Where do intermolecular forces exist?

Answer 23

Simple molecular bonds only.

Question 24

How do you determine whether a bond is polar or non-polar?

Answer 24

If it has no difference in electronegativity or is symmetrical it is non-polar.

Question 25

How do you know if a molecule is symmetrical?

Answer 25

If the central atom is bonded to the same atom and contains no lone pairs (square planar is also symmetrical).

Question 26

How do VDW occur?

Answer 26

Electrons are constantly moving so the charge can change distribution at any time. One side of a molecule could become more negative than the other which is a temporary dipole. This induces a dipole in another molecule and there’s an attraction between the delta positive on one molecule and delta negative on another adjacent molecule.

Question 27

What affects the strength of VDW?

Answer 27

Size (bigger=more), Surface area contact (more SA=more VDW).

Question 28

How does a permanent dipole-dipole force occur?

Answer 28

There is an attraction between a delta positive on one molecule and a delta negative on an adjacent molecule.

Question 29

What do hydrogen bonds occur in?

Answer 29

Polar molecules which have a hydrogen directly bonded to oxygen, nitrogen or fluorine.

Question 30

Why do hydrogen bonds form?

Answer 30

O, N and F are the most electronegative atoms so they pull the pair of electrons in the bond very strongly towards themselves. The lone pair on the adjacent molecule is then attracted to the very delta positive hydrogen.

Question 31

How do hydrogen bond diagrams have to be drawn?

Answer 31

Linear.

Question 32

Why is ice less dense than water?

Answer 32

There are fewer particles of water per unit of volume in the solid state than liquid because in ice the molecules are further apart than in liquid.

Question 33

What is the order of strength for intermolecular forces?

Answer 33

Hydrogen bonding > permanent dipole-dipole > VDW.

Question 34

What is the structure of diamond and graphite?

Answer 34

Diamond- Strong covalent bonds between C atoms. Graphite- Strong covalent bonds between C atoms and weak VDW forces between layers, also has delocalised electrons.