Bonding and Structure

Question 1

what type of ions will metals always form

Answer 1

cations

Question 2

define ‘metallic bond’

Answer 2

the strong electrostatic attraction between metal ions and a sea of delocalised electrons

Question 3

define ‘metallic radius’

Answer 3

half the distance between the centers of two adjacent metal ions in a metallic lattice

Question 4

in terms of melting temperature, how does this change with metallic radii

Answer 4

the smaller the metallic radius, the greater the melting point

Question 5

name 6 chemical properties of metals

Answer 5

• smaller first ionisation energy than non-metals in the same period
• have the lowest electronegativity levels in the periodic table
• low electronegativity and first IE means its more energetically feasible to lose electrons in bonding
• react with dilute acids to form hydrogen gas and a solution of a salt
• react with water to form an alkaline solution of a metal hydroxide and hydrogen gas
• a more reactive metal will reduce the ions of a less reactive metal

Question 6

define an ionic bond

Answer 6

the strong electrostatic attraction between oppositely charged ions

Question 7

what is the octet rule

Answer 7

when ions are formed they normally have a full outer shell (like that of a noble gas)

Question 8

properties of ionic bonds (4)

Answer 8

• high melting and boiling points
• brittle and easily cleaved (split)
• soluble in water
• electrical and thermal conductors when molten or in solution

Question 9

what happens when ionic bonds are hydrated

Answer 9

hydrogen is attracted to the negative ions and oxygen is attracted to the positive ions in the bond

Question 10

why do ionic bonds have a high melting and boiling point

Answer 10

because of the strong electrostatic attraction between the oppositely charged ions, it requires lots of energy to overcome

Question 11

what is the melting point determined by in ionic bonding

Answer 11

the strength of the ionic bonds

Question 12

name three factors effecting the strength of ionic bonds

Answer 12

• the size of the ionic radius (smaller size means a greater strength)
• charge of the ions (higher charge, greater strength)
• the surface area

Question 13

why does ionic radius increase down a group

Answer 13

the number of shells the ion contains increases

Question 14

what is it called when ions have identical electron configurations

Answer 14

isoelectronic

Question 15

why does ionic radius decrease from N3- to Al3+

Answer 15

the number of protons increases this increases the nuclear charge. so, the electrons face a stronger force of attraction to the nucleus, decreasing the ionic radius

Question 16

define a covalent bond

Answer 16

the strong electrostatic attraction between the nuclei of two atoms and the shared pair of electrons between them

Question 17

what is a dative covalent/coordinate bond

Answer 17

a bond formed where one atom donates two electrons to an atom or ion

Question 18

give two examples of molecules with a dative bond

Answer 18

ammonium, carbon monoxide

Question 19

what are dative covalent bonds represented with

Answer 19

an arrow

Question 20

give an example of a molecule with a single covalent bond

Answer 20

H-F

Question 21

give an example of a molecule with a double covalent bond

Answer 21

O=O

Question 22

give an example of a molecule with a triple covalent bond

Answer 22

N=-N

Question 23

define bond enthalpy

Answer 23

the energy required to break a particular covalent bond of one mole of a molecule in gaseous state (strength of a covalent bond)

Question 24

shorter covalent bond. higher or lower bond enthalpy?

Answer 24

higher

Question 25

what two forces determine bond length of a covalent bond

Answer 25

attraction (positive nuceli-negative electrons) repulsion (two positive nuclei + negative electrons)

Question 26

how is a high bond enthalpy created

Answer 26

greater electron density between atoms results in stronger forces of attraction. atoms are pulled closer to each other, shorter bond=high bond enthalpy

Question 27

which has a higher bond enthalpy H-F or N=-N

Answer 27

N=-N (greater electron density, shorter bonds)

Question 28

Name 4 giant covalent structures

Answer 28

- graphite - diamond - graphene - silicone dioxide

Question 29

Properties of graphite

Answer 29

- insoluble - good electrical conductor - low density - very high melting point - lubricant

Question 30

Why is graphite insoluble

Answer 30

Due to the strong covalent bonds between the carbon atoms

Question 31

Why does graphite have a low density

Answer 31

Due to its layers being far apart

Question 32

Why can graphite conduct electricity

Answer 32

Each carbon atom is bonded to three other carbon atoms. That leaves a delocalised electron as the fourth. This can carry a charge throughout the layers

Question 33

Why does graphite have a very high melting point

Answer 33

Due to the strong covalent bonds between the carbon atoms

Question 34

Properties of diamond (4)

Answer 34

- good thermal conductor - poor electrical conductor - insoluble - high melting point

Question 35

Why is diamond a good thermal conductor

Answer 35

It’s tightly packed, rigid arrangement allows for thermal energy to pass easily

Question 36

Why is diamond a poor electrical conductor

Answer 36

Each carbon atom is covalently bonded to four others In a tetrahedral shape. This means there are no delocalised electrons so no charge can be carried.

Question 37

Why is diamond insoluble

Answer 37

Due to the strong covalent bonds between carbon atoms, they are too strong to break

Question 38

Why does diamond have a very high melting point

Answer 38

Contains strong covalent bonds between the carbon atoms

Question 39

What giant covalent structure has a similar shape and properties to diamond

Answer 39

Silicone IV dioxide

Question 40

What are the properties of graphene (3)

Answer 40

- lightweight and transparent - good electrical conductor - high strength properties

Question 41

Why is graphene lightweight and transparent

Answer 41

It’s one layer of graphite made up of hexagonal rings but only one atom thick

Question 42

Why is graphene a good electrical conductor

Answer 42

Contains delocalised electrons (carbon covalently bonded to only three other carbons)

Question 43

Why does graphene have high strength properties

Answer 43

Delocalised electrons strengthen the covalent bonds between carbon atoms

Question 44

What is graphene used in (3)

Answer 44

- aircraft shells - super computers/high speed computers - smart phone screens

Question 45

How do covalent bonds become polar

Answer 45

If the atoms attached to it have a difference in electronegativity

Question 46

In terms of polarity, a bigger difference in electronegativity=

Answer 46

A more polar bond

Question 47

Give two examples of polar molecules

Answer 47

Hydrogen chloride Water

Question 48

Why is H-Cl polar

Answer 48

The chlorine atom is more electronegative, electrons shift closer to the chlorine H—;Cl

Question 49

Is Cl-Cl polar and why

Answer 49

No because the chlorine atoms are bonded with the same electronegativity values so the shared electrons sit in the middle Cl-;-Cl

Question 50

Why is water polar

Answer 50

Because it is unsymmetrical

Question 51

Is CO2 polar and why

Answer 51

No because it is a symmetrical molecule O;=C=;O

Question 52

What makes covalent molecules non polar

Answer 52

If the molecule is bonded with the same/similar electronegativity values, the shared electrons will sit in the middle of the bond. Furthermore if the molecule is symmetrical.

Question 53

how strong is the repulsion between two bonding pair electrons

Answer 53

low

Question 54

how strong is the repulsion between a lone pair and a bonding pair electron

Answer 54

medium

Question 55

how strong is the repulsion between two lone pair electrons

Answer 55

high

Question 56

how do lone pair electrons affect the shape of the molecule

Answer 56

they push bonding pairs closer together, for every lone pair the bonding angle reduces by 2.5degrees

Question 57

what is electronegativity

Answer 57

the ability of an atom to attract an electron pair

Question 58

why do molecules with more electrons have larger London dispersion forces

Answer 58

- they will have larger fluctuations in electron density - leads to larger temporary dipoles, and stronger dipole-dipole interactions

Question 59

what type of molecules do you find permanent dipole-dipole interactions between

Answer 59

polar molecules

Question 60

where do you find hydrogen bonds

Answer 60

when hydrogen atoms form a strong permanent dipole-dipole interaction between either nitrogen, oxygen or fluorine

Question 61

name three examples of liquids with hydrogen bonds

Answer 61

water hydrogen fluoride ammonia

Question 62

why do hydrogen bonds form

Answer 62

when hydrogen is bonded to an extremely electronegative element is forms a strong delta plus charge. due to its small size, hydrogen has a high charge density so it can form a strong bond with any highly delta negative atom