2 - Bonding And Structure

Question 1

Giant covalent bonds?

Answer 1

Giant regular lattice
Sharing of electrons
Always solid at room temperature
Hard
Insoluble

Question 2

Graphite?

Answer 2

Arranged in layers
each atom is bonded to 3 other atoms
Conductive

Question 3

Small covalent molecules?

Answer 3

Low melting and boiling points because of weak intermolecular forces which break down easily.
Non conductive
Strong bonds between atoms, weak bonds between molecules
low melting and boiling points
Insulators

Question 4

Metallic bonding?

Answer 4

Malleable because they’re in layers
Sea of delocalised electrons, free to move throughout.
sharing of many detatched electrons between positive ions.
This gives them structure and explains why many metals have high boiling points

Question 5

Define metallic bonding?

Answer 5

Is the force of attraction, between valence electrons and metal atoms

Question 6

Ionic bonding?

Answer 6

Between a metal and a non metal.
Between atoms which give or receive electrons.
DON'T conduct when solid
Soluble
High melting and boiling points

Question 7

Structure of ionic bonding?

Answer 7

Lattice structure
Regular ion arrangement, results in crystals being produced.
Electrostatic forces of attraction between ions, means a lot of energy is required to separate negative and positive ions.

Question 8

Proving existence of ions?

Answer 8

The migration of coloured ions during the electrolysis of copper (11) and chromate (v1) solution.

Potassium manganate and the DC current

Question 9

Electron repulsion theory?

Answer 9

Greatest forces of repulsion:
Lone pair lone pair
lone pair bonded pair
Bonded pair bonded pair

Question 10

Lone pairs?

Answer 10

Repel as much as possible.
Take off 2.5 degrees for every lone pair
Affect the bond angle.

Question 11

Shapes of molecules?

Answer 11

Depends on the number of pairs of electrons in the outer shell.
All shapes depends on the number of pairs!

Question 12

Linear?

Answer 12

2 pairs

180 degree bond anlge

Question 13

Trigonal planar?

Answer 13

3 pairs

120 degrees

Question 14

Tetrahedral?

Answer 14

4 pairs

104.5, 107, 109.5 degrees depending on lone pairs

Question 15

Trigonal bipyramid?

Answer 15

5 pairs

90, 120, 180 degrees

Question 16

Octahedral?

Answer 16

6 pairs

90, 180 degrees

Question 17

What are the most electronegative elements?

Answer 17

N,O,F

nitrogen, oxygen, flourine

Question 18

Define electronegativity?

Answer 18

Is the tendancy to attract the shared pair of electrons

Question 19

Dative bonds?

Answer 19

Are formed when an ion attaches to the lone pair of an atom

Question 20

Non polar molecules, eg O2?

Answer 20

Oxygen have the same electronegativity, therefore the electrons are equally shared between the atoms

Question 21

Polar molecules eg, H2O?

Answer 21

Oxygen has a higher electronegativity than hydrogen, so the electrons will spend more time closer to the oxygen atom. This results in a partial negative charge around the oxygen atom.

Question 22

What did Pauling do?

Answer 22

Assigned every element its electronegativity.

Question 23

London Forces?

Answer 23

Occur between all molecules.
Fleeting repulsions and attraction between nuclei of the atoms and the electron cloud.
Temporary displacement cause temporary dipoles.
Neighbouring molecules are induced with temporary dipoles (opposite charge)

Question 24

Dipole, dipole?

Answer 24

Attractive forces between the positive end of 1 polar molecule and the negative end of another.
Occurs between 2 polar substances
Creates a semi charge, or dipole in molecule
effected by: electronegativity of atoms and number of electronegative atoms

Question 25

Hydrogen bonding?

Answer 25

Occurs between molecules where hydrogen is bonded to N,O,F
There must be a lone pair of electrons
Always a bond angle of 180.

Question 26

Polarity?

Answer 26

If the shape is symmetrical and the electrons are the same, it’s non polar!

Question 27

Solubiltiy?

Answer 27

Like dissolves like,,,
Polar dissolves polar
Non polar dissolves non polar

Question 28

Why do polar solvents dissolve in polar substances?

Answer 28

because the partial charges in the polar solvent can hold onto the partial charges in the polar solute and dissolve.

Question 29

Non polar and polar?

Answer 29

Won’t dissolve with eachother because the molecules would rather remain, and use their partial charges to stick together with hydrogen bonds than with the non polar molecules.

Question 30

Bond length and strength?

Answer 30

x ray diffraction allows chemists to look at structures. Microwave spectroscopy can give us info on bond angles.

Question 31

Testing polarity?

Answer 31

Charge a plastic rod, and hold next to a stream of the chemical you want to test, if its polar it will diffract!

Question 32

Electronegativity patterns?

Answer 32

INCREASES across the periodic table

INCREASES up the groups

Question 33

Why does electronegativity increase up a group?

Answer 33

There are more protons in the nucleus so it has a stronger pull

Question 34

Why does electronegativity increase across the periodic table?

Answer 34

More shells, and therefore electrons are further away from the nucleus! they want to gain electrons

Question 35

Polar bonds in a molecule?

Answer 35

polar bonds in a molecule does not mean the molecule has to be polar, if the moleules are symmetrical, then the dipoles cancel.