Bonding And Structure

Question 1

Ionic bonding

Answer 1

The electrostatic force of attraction between oppositely charged ions, formed by electron transfer
It holds together cations and anions in ionic compounds

Question 2

Common cations?

Answer 2

Metal ions- Na + and Al 3+

Ammonium ions -NH3+

Question 3

Common anions

Answer 3

Non metal ions - cl- or o2-

Polyatomic ions ( no3-, so42-)

Question 4

What are ionic compounds

Answer 4

Ionic bonding leads to GIANT IONIC STRUCTURES/ LATTICES

CLOSEly packed, regular arrangements of positive and negative ions - where there are strong forces of attraction between the oppositely charged ions in ALL directions

Question 5

Describe a lattice of Na and Cl ions

Answer 5

Each Na+ is surrounded by 6 cl-

And each cl- is surrounded by 6 Na+

Question 6

Properties of ionic compounds

Answer 6

High melting and boiling points
Solubility
Electrical conductivity

Question 7

What are the melting and boiling points liked in ionic compiunds and why ?

Answer 7

Almost all ionic compounds are solids at room temperature-there is INSUFFICIENT energy to overcome strong electrostatic forces of attraction between oppositely charged ions
High temperatures are needed to overcome this attraction

IONIC BONDIGN IS STRONGER AND M+BP IGHER , WEN IONS ARE SMALLER OR HAVE JIGHER CHARGES

Question 8

Solubility of ionic compounds

Answer 8

Many ionic compounds dissolve polar solvents , such as water
Polar h20 molecules brea down the lattice and surround each ion is solution
In a compound Mae of IONS with LARGE charges, the ionic attraction may be TOO strong for water to be able to break down the lattice structure- the compound will then not be very soluble

Question 9

What does solubility mean

Answer 9

The ionic lattice must be broken down
Water molecules must attract and surround the ions

The solubility therefore depends on relative strengths of attraction WITHIN the giant ionic lattice and the attractions between ions and h20 molecules

Question 10

Electrical conductivity - ionic compounds

Answer 10

Melted or dissolved in water

• solid lattice breaks down
• ions free to move as mobile charge carries

Question 11

Covalent bonding?

Answer 11

The strong electrostatic attraction between SHARED pair of electrons and the nuclei of the bonded atom

Question 12

Covalent BONDiNG occurs between atoms in..

Answer 12

Non metallic elements e.g. H2 and c2
Compounds of non metallic elements e.g. H2o and co2
Polyatomic ions e.g. NH4+

Question 13

What is a polyatomic ion?

Answer 13

Created when many atoms come together to form a group
Positive or negative charge
Can be cation or anion

Question 14

What is orbital overlap ( covalent bonding)

Answer 14

A covalent bond is the overlap of atomic orbitals each containing 1 electron, to give a shared pair of electrons
E.G. H + H – h2
The shared pair of electrons is attracted to the nuclei of BOTH the bonding atoms, the bonded atoms often have other shells with the same electron structure on the nearest noble gas

Question 15

A covalent bond is .. LOCALISED?

Answer 15

The attraction is localised
Acting solely between the shared pair of electrons and the nuclei of the 2 bonded atoms
The result is a small unit called a molecule

Question 16

Double covalent bond

Answer 16

Electrostatic attraction between 2 shared pairs of electrons and the nuclei of the bonding atoms
E,g, h20 and o2

Question 17

Triple covalent bond

Answer 17

The electrostatic attraction is between 3 shared pairs of electrons and the nuclei of the bonding atoms

Question 18

Dative covalent bonds /coordinate bond

Answer 18

Forms when the shared pair of electrons in the covalent bond come from ONLY ONE of the bonding atoms
The shared electron pair was originally a lone pair of electrons on one of the bonded atoms

E.g. NH4+ —- NH3 and a H+ ion

Question 19

What is average bond enthalpy?

Answer 19

Measure of covalent bond strength

Question 20

Giant adn simple covalent

Answer 20

***(

Question 21

What is the electron pair repulsion theory

Answer 21

An electron has a negative charge, so electron pairs repel one another
The electron pairs surrounding a centeral atom determine the shape of the molecule or ion
The electron pairs repel one another so they are arranged as far apart as possible
The arrangement of electron pairs minimises repulsion and thus holds the atoms in place
Different numbers o electron pairs result in different shape

Question 22

What shape do you get , when there are 2 electron bondingpairs around centeral atom ?

Answer 22

LINEAR

180 degrees

Question 23

What shape and angle for 3 bonding pairs around centeral atom

Answer 23

TRIGONAL PLANAR

120

Question 24

What shape and angle for 4 bonding pairs around centeral atom

Answer 24

Tetrahedral

109.5

Question 25

What shape and angle for 6 bonding pairs around centeral atom

Answer 25

Octahedral

90 degrees

Question 26

What are lone pairs and how do they affect bond Angels

Answer 26

Lone pairs are closer to the nucleus and occupies MORE SPACE- repel more strongly
Reduce bond angles by 2.5 per lone pair

Question 27

H20 bond angle size

Answer 27

104.5

Question 28

NH3 bond angle size

Answer 28

107

Question 29

1 lone pair + 3 bonded =

Answer 29

Pyramidal
107 degrees
E.g. NH3

Question 30

2 lone pairs + 2 bonded pair

Answer 30

Non linear
104.5
E.g. H20

Question 31

Multiple bonds?

Answer 31

Each multiple bond is treated as a bonding region or pair

Co2- 2 bonding regions - linear

Question 32

Drawing 3D structures- what are the 3 different lines

Answer 32

• solid line
• solid wedge
• dotted wedge

Question 33

Solid line ?

Answer 33

Bond in the plane of the paper

Question 34

Solid wedge

Answer 34

Comes out of the plane of the paper

Question 35

Dotted wedge

Answer 35

Goes into the plane of the paper