Topic 3- Chemical Bonding

Question 1

What are the types of bonds?

Answer 1

Chemical and physical

Question 2

What is a chemical bond?

Answer 2

When elections are gained lost or shared between atoms

Question 3

What are the types of chemical bonds?

Answer 3

A) ionic bonds (electrovalent)
B) Covalent and dative covalent bonds
C) Metallic bonds

Question 4

What are the types of physical bonds?

Answer 4

a) Hydrogen bonds
b) Permanent dipole - permanent dipole interaction
c) Induced dipole - induced dipole interaction

Question 5

What are physical bonds?

Answer 5

Bonds produced from changes of state that are broken if you go back the other way

Van der Waals bonds and Intermolecular bonds

Question 6

How do you identify ionic bonds?

Answer 6

Formula should have metallic and non metallic elements
Formula should have polyatomic ions (SO4^2-)

Question 7

How are ionic bonds produced?

Answer 7

1. The metallic element loses its valency electrons to form cations (ionisation)
   2 . The non-metallic elements gain electrons into their valency shells whereby the number gained is equivalent to their valency, to form anions
   3 . The oppositely charged ions electrostaticaly attract each other to form ionic bond. This is an exothermic reaction and the energy given out is known as lattice energy

Question 8

What are isoelectric ions?

Answer 8

Ions that have the same number of electrons

Question 9

How do you identify ionic compounds practically?

Answer 9

1 . All ionic compounds are soluble in water
2 . All ionic compounds conduct electricity when in molten state or aqueous phase
3 . Ionic compounds have high melting points due to strong electrostatic forces
4 . They are hard but brittle

Question 10

What is an ionic bond?

Answer 10

A strong electrostatic bond between oppositely charged ions

Question 11

Metallic bonding

Answer 11

The electrostatic attraction between positive ions and delocalised electrons

Question 12

Covalent bonding

Answer 12

Electrostatic attraction between the nuclei of two atoms and a shared pair of electrons

Question 13

How to identify ionic compounds practically

Answer 13

• Soluble in water
• Conduct electricity only when molten or aqueous
• High melting points
• Hard
• Brittle - when ions with the same charge get close, repulsion causes breakage without warning

Question 14

Define

Electronegativity

Answer 14

The ability or affinity for an atom to attract electrons to itself

Question 15

Explain the reactivity of free radicals

Answer 15

they have one electron to be readily lost to allow for pairing

Question 16

Why are pi bonds easier to break than sigma bonds?

Answer 16

Electrons in a pi bond are farther from the nucleus than sigma bonds, therefore they are less strongly held

Question 17

Describe

Excited state

Answer 17

when one electron gains energy and jumps to a higher energy level

Question 18

What are degenerate orbitals?

Answer 18

Orbitals at the same energy level

Question 19

Conditions for a Dative Covalent bond

Answer 19

• One species mus have a lone pair
• The other species must have an empty orbital
• the atoms must have opposite charges

Question 20

What are ligands?

Answer 20

a species that donates lone pairs of electrons into a single metal cation

Question 21

What is a polar bond?

Answer 21

A covalent bond with ionic charachter

Question 22

Relate Nuclear Charge to Electronegativity

Answer 22

the higher the nuclear charge the more stronger the attraction to electrons therefore the higher the electronegativity

electronegativity increases across the period

Question 23

Relate the shielding effect to electronegativity

Answer 23

The more shells, the more that nuclear charge is shielded, therefore the lower the electronegativity

electronegativity reduces down the group

Question 24

Conditions for Polar bonds

Answer 24

• Must have polar bonds (covalent with charges)
• must be asymmetrical so that dipoles do not cancel out

difference in electronegativity value between 04 and 1.7

all polar molecules are soluble in water

Question 25

Conditions for non-polar molecules

Answer 25

• Must have non-polar bonds
• symmetrical if they have polar bonds

all hydrocarbons; insoluble in water

Question 26

Parts of metallic bonds

Answer 26

• Layers of cations
• Sea of delocalised valency electrons
• network of stong electrostatic forces

Question 27

Metallic Bonding

Evidence of layers of cations

Answer 27

Metals are malleable and ductile because the layers can slide over each other

Question 28

Metallic bonding

Evidence of delocalised electrons

Answer 28

Metals are very good conductors of electricity as the electrosn become mobile when a current is applied

Question 29

Conditions

Hydrogen Bonds

Answer 29

1. Must contain one of the highly electronegative elements ( N O F )
2. Hydrogen must be directly attached to one of the above
3. Higly electronegative elements must have a lone pair

Question 30

Why is ice less dense than water?

Answer 30

Ice forms a network of permanent hydrogen bonds with air molecules trapped within

Question 31

Factors affecting the strength of Induced dipole - Induced dipole interactions

Answer 31

Size of the molecule
length of the moleule

increase in both leads to stronger bonds

Question 32

VSEPR Theory

Answer 32

Valence Shell Electron Pair Repulsion Theory

Question 33

What is the VSEPR theory?

Answer 33

1. Cental atom is the one in the molecule that forms the most covalent bonds
2. Must have bonding pairs
3. BPs and LPs repel echother for maximum separation for minimal repulsion
4. Double and triple bonds are treated as one centre of negative charge