Topic 2- Chemical bonding and structure

Question 1

What are the physical properties of a metal?

Answer 1

• high melting point
• good electrical conductivity
• good thermal conductivity
• malleability
• ductility

Question 2

What is metallic bonding?

Answer 2

Metallic bonding is the electrostatic force of attraction between the nuclei of the metal cations and delocalised electrons

Question 3

What is ionic bonding?

Answer 3

Ionic bonding is the strong electrostatic attraction between oppositely charged ions

Question 4

What determines the strength of the ionic bond?

Answer 4

The smaller the ions and the larger the charge on the ions the stronger the ionic bonding

Question 5

What are the physical properties of ionic compounds?

Answer 5

• high melting point
• brittle
• poor electrical conductor when solid but good when molten
• often soluble in water

Question 6

What is evidence for the existence of ions?

Answer 6

The electrolysis of copper(2)chromate(5). When green copper(2)chromate(5) is electrolysed the ions begin to separate. The copper2+ ions move towards the negative electrode and we see a blue solution. The chromate2- ions move towards the positive electrode and we see a yellow solution.

Question 7

What is a covalent bond?

Answer 7

A covalent bond is the strong electrostatic attraction between the nuclei of two atoms and the bonding pair of electrons

Question 8

What is bond length?

Answer 8

Bond length is the distance between nuclei of the two atoms that are covalently bonded together.

Question 9

How does bond length affect the strength of a covalent bond?

Answer 9

The shorter the bond length the stronger the strength of the covalent bond so the higher the bond enthalpy

Question 10

What is electronegativity?

Answer 10

Electronegativity is the eabillity of an atom to attract a bonding pair of electrons

Question 11

What are the trends in electronegativity?

Answer 11

• Electronegativity decrease when you go down a group

- Electronegativity increases across a period

Question 12

What is a polar covalent bond?

Answer 12

A polar covalent bond is a type of covalent bond between two atoms where the bonding electrons are unequally distributed

Question 13

What is a dative covalent bond?

Answer 13

It is a covalent bond in which both electrons come from the same atom

Question 14

What is a dipole?

Answer 14

A dipole is a drift of bonded electrons towards a more electronegative element

Question 15

What is the bond angle formed in a linear shape?

Answer 15

180 degrees with 2 bond pairs and 0 lone pairs e.g BeCl2

Question 16

What is the bond angle formed in a trigonal planar?

Answer 16

120 degrees with 3 bond pairs and 0 lone pairs e.g BF3

Question 17

What is the bond angle formed in a tetrahedral?

Answer 17

109.5 degrees with 4 bond pairs and 0 lone pairs e.g CH4

Question 18

What is the bond angle formed in a trigonal bipyramidal?

Answer 18

90 degrees and 120 degrees with 5 bond pairs and 0 lone pairs e.g PCl5

Question 19

What is the bond angle formed in an octahedral?

Answer 19

90 degrees with 6 bond pairs and 0 lone pairs e.g SF6

Question 20

What is the bond angle formed in a trigonal pyramidal?

Answer 20

107 degrees with 3 bond pairs and 1 lone pair e.g NH3

Question 21

What is the bond angle formed in a v-shaped?

Answer 21

104.5 degrees with 2 bond pairs and 2 lone pairs e.g H2O

Question 22

What is the bond angle formed in a square planar?

Answer 22

90 degrees with 4 bond pairs and 2 lone pairs e.g XeF4

Question 23

What are London forces?

Answer 23

These are forces between atoms and molecules. Electrons in a molecule or atom can move from one end to another creating a temporary dipole. The positive end will have forces of attraction to the negative end. Bigger the molecules the more London forces as there are more electrons.

Question 24

What are permanent Diople-Dipole?

Answer 24

There are weak electrostatic forces that exist between molecules with a polarity. The negative part of one molecule is attracted to the positive part of the other. Permanent dipoles have stronger interactions than London forces.

Question 25

What is hydrogen bonding?

Answer 25

Hydrogen bonding is the strongest intermolecular force and occurs when you have very electronegative elements. Hydrogen bonding occurs when hydrogen on one molecule forms a bond with the lone pair on nitrogen, oxygen or fluorine (3 most electronegative elements)

Question 26

What can dissolve in polar solvents?

Answer 26

Polar substances can be dissolved in polar solvents. Most ionic compound can dissolve in polar solvents like H2O. Some non-ionic substances like alcohol can dissolve in polar solvents as they can hydrogen bond with water but the hydrocarbon part which is non-polar don't dissolve

Question 27

What is a giant covalent structure?

Answer 27

These are a giant network of atoms linked to each other by covalent bonds. The most common giant covalent substances are diamond, graphite, graphene and silicon dioxide

Question 28

What is Graphite?

Answer 28

Graphite is a giant covalent structure with each carbon bonded 3 times with the 4th electron delocalised. Graphite has layers that slide easily making it slippery and a good lubricant. Delocalised electrons between the layers make graphite conduct electricity as they can carry the charge. Graphite is insoluble and has strong covalent bonds which are too strong to break hence it having a high melting point

Question 29

What is Diamond?

Answer 29

Diamond is a giant covalent structure with each carbon bonded 4 times in a tetrahedral shape. Its tight arrangement allows heat to be conducted well. Diamond is insoluble and has strong covalent bonds which are too strong to break hence it having a high melting point

Question 30

What is graphene?

Answer 30

Graphene is a single layer of graphite which is 1 atom thick. The delocalised electrons makes graphene an excellent conductor of electricity. Graphene is lightweight, transparent and strong