Ch7 Bonding and structure

Question 1

Ionic bond basic definition

Answer 1

Electrostatic attraction between oppositely charged ions(positive and negative)

Question 2

Ionic bond description

Answer 2

metal lose electron(s) from valence shell and become positive anion

electron is transferred to non-metal which becomes negative cation

Oppositely charged ions are attracted to one another and form bond

Question 3

4 Properties of giant ionic lattice

Answer 3

1. High mpt+bpt- ionic bonds are strong and occur throughout, requiring large amount of energy to overcome
2. poor conductor of electricity when solid- ions are in fixed positions and cannot move so no mobile carriers
3. good conductors of electricity when molten- ions are mobile and free to move
4. soluble in water and polar solvents

Question 4

Hydration of ionic solids

Answer 4

some ionic solid are soluble in water

the atoms have charges which are attracted to polar water molecules and bind to them

energy released as bonds are formed is enough to compensate energy needed to overcome ionic bonds

Question 5

Insoluble ionic solids

Answer 5

Energy needed to be released when ions are hydrated is not sufficient to balance energy required to separate ions

Question 6

Covalent bond basic definition

Answer 6

electrostatic attraction between shared pair of electrons and nuclei of two bonded atoms

Question 7

Covalent bond description

Answer 7

Adjacent non-metal atoms share electrons in valence shells to achieve full outer shells

Question 8

Dative covalent bond

Answer 8

two atoms share two electrons but one atom provides both electrons from a lone pair

e.g. NH3 + H+ -> NH4+

Question 9

Lone pair of electrons

Answer 9

1. can form variations on covalent bond- dative covalent bond
2. affect shape of molecules
3. can behave as nucleophiles in organic reactions

Question 10

3 Properties of covalent compounds

Answer 10

1. low mpt + bpt - attraction between discrete, separate neighbouring covalent molecules are weak so small amount of energy required to overcome
2. poor conductor electricity - no mobile charge carries, ions or electrons
3. soluble in non-polar solvents

Question 11

Electron pair repulsion theory

Answer 11

Electron pairs repel each other as far apart in space as possible around central atom

shape of molecule depends upon number and type of electron pairs around the central atom

Lone pairs repel more than bonded pairs(subtract 2.5° in bond angle)

Question 12

Shape of molecules with 2 bonded pairs and no lone pairs

Answer 12

Linear
Bond angle 180°

Question 13

Shape of molecules with 3 bonded pairs and no lone pairs

Answer 13

Trigonal planar
Bond angle 120°

Question 14

Shape of molecules with 4 bonded pairs and no lone pairs

Answer 14

tetrahedral
bond angle 109.5°

Question 15

Shape of molecules with 5 bonded pairs and no lone pairs

Answer 15

Trigonal bipyramidal
Bond angle 120° and 90°

Question 16

Shape of molecules with 6 bonded pairs and no lone pairs

Answer 16

Octahedral
Bond angle 90°

Question 17

Shape of molecules with 3 bonded pairs and 1 lone pair

Answer 17

Pyramidal
Bond angle 107°

Question 18

Shape of molecule with 2 bonded pairs and 2 lone pairs

Answer 18

Angular(bent)
Bond angle 104.5°

Question 19

Metallic bond basic definition

Answer 19

Electrostatic attraction between delocalised electrons and positive ions held within the lattice

Question 20

Delocalised electrons

Answer 20

Bonding electrons that are not fixed between two atoms in a bond
Mobile and are shared by several atoms

Question 21

3 properties of metallic structures

Answer 21

1. high mpt + bpt- large amount of energy needed to overcome many strong metallic bonds
2. good conductor of electricity- contains mobile charge carriers(sea of delocalised electrons) that are free to move
3. malleable and ductile- nondirectional, independent of shape and exists in all directions

Question 22

electronegativity

Answer 22

the tendency of an atom to attract the shared pair of electrons in a covalent bond

Question 23

Bond polarity

Answer 23

when pair of electrons making up asymmetrical covalent bond aren’t shared evenly between the atoms

ionic character when there is a difference in electronegativity in two atoms forming covalent bond

creates a dipole bond

Question 24

Two trends in electronegativity

Answer 24

1. Increases across a period
2. Decreases down a group

Question 25

symmetrical shapes

Answer 25

linear, trigonal planar, tetrahedral and octahedral

Question 26

asymmetrical shapes

Answer 26

pyramidal and angular(bent)

Question 27

Intermolecular forces

Answer 27

forces of attraction that occur between molecules

Question 28

Permanent dipole-dipole interactions

Answer 28

weak electrostatic forces between dipoles of neighbouring molecules

Question 29

Hydrogen bonds

Answer 29

relatively strong electrostatic attractions between polar molecules (that contain hydrogen and has lone pair) covalently bonded to elements with higher electronegativity e.g. F, O, N

Question 30

Examples of hydrogen bonds

Answer 30

water H2O
ammonia NH3
hydrogen fluoride HF
compounds with -OH group
compounds with -NH2 group

Question 31

Water propertied due to hydrogen bonds

Answer 31

1. solid ice is less dense than liquid water - h20 molecules hydrogen bond to form interlocking hexagonal rings, so are held further apart creating greater volume and lower density
2. water has high mpt + bpt - additional energy required to overcome large amount of hydrogen bonds

Question 32

Induced dipole-dipole interactions

Answer 32

Temporary movement of electrons generates an instantaneous dipole

This induces other dipoles in neighbouring molecules

Two dipoles generate a weak temporary force of attraction between molecules

• weakest intermolecular force
• larger amount of electrons, greater number of forces