Bonding & Structure

Question 1

what are the three main types of bonding?

Answer 1

ionic, covalent & metallic

Question 2

what is ionic bonding?

Answer 2

electrostatic attraction between positive and negative ions 
ions are formed through electron transfer from metals to non-metals

Question 3

what is metallic bonding?

Answer 3

electrostatic attraction between metal cations and delocalised electrons

Question 4

what is covalent bonding?

Answer 4

electrostatic attraction between the shared pair of electrons and the nucleii involved
between non-metals

Question 5

what is a dative covalent bond?

Answer 5

where one of the atoms contributes both atoms

Question 6

what is complicated bonding?

Answer 6

negative ions have extra electrons from elsewhere to create the overall charge - displayed as a different symbol (eg- triangle)

Question 7

when does the octet rule not apply?

Answer 7

incomplete octet
expanding the octet

Question 8

what is a lattice?

Answer 8

an infinite and repeating arrangement of particles formed by ions


Question 9

what are the properties of ionic compounds?

Answer 9

• high melting point
• strong electrostatic attraction between ions
• conduct when molten / dissolved in aqueous solution
• hard & brittle

Question 10

what are the properties of metals?

Answer 10

• can carry charge in every state
• high melting and boiling point
• strong electrostatic attraction
• malleable & ductile

Question 11

what are properties of giant covalent substances?

Answer 11

eg - diamond
- high melting and boiling point
- no electrical conductivity
- strong & brittle

Question 12

what are properties of giant covalent layered structures?

Answer 12

eg - graphite
- high melting and boiling point
- layers that can move and carry charge so can conduct
- soft due to weak intermolecular forces 

Question 13

what are the properties of simple molecular structures?

Answer 13

eg - iodine
- low melting point
- poor electrical conductivity
- soft due to weak intermolecular forces

Question 14

what are the two types of electron pairs?

Answer 14

bonding pairs
lone pairs

Question 15

how do you calculate the shape of a molecule?

Answer 15

• number of outer shell electrons on the central atom
• one electron for each atom bonded
• add together ( + charge if there is one)
• = total electrons (divided by two = electron pairs)

Question 16

molecule shape with two pairs of electrons?

Answer 16

linear

Question 17

molecule shape with three pairs of electrons?

Answer 17

trigonal planar

Question 18

molecule shape with four pairs of electrons?

Answer 18

tetrahedral

Question 19

molecule shape with six pairs of electrons?

Answer 19

octahedral

Question 20

molecule shape with three pairs and one lone pair?

Answer 20

bent

Question 21

molecule shape with four pairs and one lone pair?

Answer 21

pyramidal

Question 22

molecule shape with six pairs and one lone pair?

Answer 22

square based pyramid

Question 23

molecule shape with four pairs and two lone pairs?

Answer 23

bent

Question 24

molecule shape with six pairs and two lone pairs?

Answer 24

square planar

Question 25

what is the general rule between lone and bonding pairs?

Answer 25

the bond angle between the bonding pairs of electrons is reduced by about 2.5° for every lone pair present

Question 26

how do you explain shapes and angles?

Answer 26

- electron pairs repel and arrange to minimise repulsion - how many electron pair regions of each type are there? - lone pairs repel more than bonded pairs - calculate shape & bond angle

Question 27

what is electronegativity?

Answer 27

the power of an atom to attract electrons in a covalent bond it has no units

Question 28

what is a polar bond?

Answer 28

when an electron pair is displaced towards the more electronegative atom creating an electric dipole

Question 29

what are the three types of intermolecular force?

Answer 29

- london forces - permanent dipole-dipole interactions - hydrogen bonding

Question 30

tell me about london forces

Answer 30

- found in any simple structure - create temporary dipoles and temporary induced dipoles - weak - strength depends on the number of electrons in the molecule & the surface area of the molecule (shape)

Question 31

how do you explain the origin of london forces?

Answer 31

- random movement creates an uneven distribution of electrons - creates a temporary dipole in the molecule - induces a temporary induced dipole in a neighbouring molecule

Question 32

how do you explain the differences in boiling points of simple structures?

Answer 32

- molecule has more electrons / molecule has larger surface area so more points of contact - stronger london forces - more energy required to overcome the forces

Question 33

tell me about permanent dipole-dipole interactions

Answer 33

- caused by polar bonds in nonsymmetrical molecules - boiling points of the compounds are slightly higher than expected - slightly increases the strength of the intermolecular forces

Question 34

tell me about hydrogen bonding

Answer 34

- strongest form of intermolecular bonds - only occur when there is a hydrogen bonded directly to an oxygen, nitrogen or fluorine - creates relatively high boiling points - explains why ice has a low density and the helical nature of DNA