Structure and Bonding 1 - Types of Bonding

Question 1

what do atoms want to achieve when bonding and why?

Answer 1

a full outer shell, in order to achieve a noble gas configuration, (most stable)

Question 2

how is an ionic bond formed?

Answer 2

a metal transferring electrons to a non-metal

Question 3

define ionic bond

Answer 3

the bond that is caused by the electrostatic attraction between a positively charged ions (cations) and a negatively charged ions (anions) in a lattice

Question 4

give the charge on a sulphate ion

Answer 4

SO4 2-

Question 5

give the charge on a hydroxide ion

Answer 5

OH -

Question 6

give the charge on a nitrate ion

Answer 6

NO3 -

Question 7

give the charge on a carbonate ion

Answer 7

CO3 2-

Question 8

give the charge on an ammonium ion

Answer 8

NH4 +

Question 9

how do you tell the charge of an ion using the periodic table?

Answer 9

group 1 = +1
group 2 = +2
group 7 = -1
group 6 = -2 etc

Question 10

which 2 factors affect the strength of an ionic bond? what can these be refered to as together?

Answer 10

the size of ions and the magnitude of charge on ions, can be taken together as SURFACE CHARGE DENSITY, charge / SA

Question 11

how does the size of an ion affect the strength of an ionic bond?

Answer 11

charges closer together will form stronger electrostatic forces

Question 12

how does the magnitude of charge on an ion affect the strength of an ionic bond?

Answer 12

ions with higher charged will form stronger electrostatic forces

Question 13

describe the structure of an ionic crystal

Answer 13

a giant crystalline lattice composed of repeating positive and negative ions

Question 14

explain what the coordination number in NaCl is a why?

Answer 14

coordination number = 6
because in the 3D lattice each Na+ is in contact with 6Cl-

Question 15

describe the position and movement of ions in a solid ionic compound.
what happens when a solid ionic compound is heated?

Answer 15

in a solid ionic compound the IONS are not free to move, and vibrate about a fixed position.
when a solid ionic compound is heated the ions vibrate more strongly, and are free to move

Question 16

state the 4 properties of ionic compounds

Answer 16

1) high melting points
2) don’t conduct when solid
3) conduct when molten or aqueous
4) often water soluble

Question 17

explain why ionic compounds have high melting points

Answer 17

the strong electrostatic forces of attraction between oppositely charged ions requires a lot of energy to overcome

Question 18

explain why ionic compounds don’t conduct electricity when solid

Answer 18

the ions are about fixed positions throughout the lattice and so cannot move or carry charge

Question 19

explain why ionic compounds conduct electricity when molten or aqueous

Answer 19

ions are free to move and carry charge throughout the structure

Question 20

state the test for an ionic compound.
how do you spot one?

Answer 20

electrolyse it
it will conduct when molten or aqueous but not when solid, and consists of a metal and a non-metal

Question 21

how is a covalent bond formed?

Answer 21

when atoms share pairs of electrons

Question 22

define covalent bond

Answer 22

the bond that is formed by a shared pair of electrons between 2 non-metals

Question 23

state the two types of covalent molecules

Answer 23

simple molecular and giant covalent (macromolecular)

Question 24

what’s the one thing to remember when drawing dot and cross diagrams?

Answer 24

the group which an element occupies dictates the number of electrons that it has in its outer shell in its natural state eg. group 7 will have 7e- in its outer shell

Question 25

define lone pair

Answer 25

a lone pair of electrons is a pair of electrons which are not used in bonding

Question 26

define bonding pair

Answer 26

a bonding pair of electrons is a pair of electrons which are used in bonding

Question 27

draw dot and cross diagrams for the following, and circle the lone pairs of electrons in each: H2 Cl2 H2O NH3 CH4

Answer 27

(check against notes)

Question 28

what is meant by an electron deficient atom and give an example

Answer 28

an electron deficient atom is one which does not manage to share 8 electrons when forming a compound, eg. Be in BeCl2

Question 29

identify the electron deficient atom in the following BF3 AlCl3

Answer 29

(check diagrams against notes if used) B Al

Question 30

why do some atoms have more than 8 electrons in their outer shell?

Answer 30

because they use vacant 3d orbitals

Question 31

which atoms use vacant 3d orbitals in the following PCl5 SF6

Answer 31

(check diagrams against notes if used) P and S use vacant 3 d orbitals

Question 32

define dative covalent/coordinate bonding

Answer 32

a covalent bond where one element provides both of the bonding pair of electrons

Question 33

state the requirement for a dative covalent bond

Answer 33

an atom or molecule which is electron rich, and one which is electron deficient

Question 34

explain how a dative covalent bond is formed

Answer 34

the element with the lone pair donates both to the deficient atom to form a new dative covalent bond

Question 35

which alternative notation can be used for dative covalent bonds and what is its convention?

Answer 35

arrows show where electrons are being donated TO, beginning from the electron rich atom/molecule and ending up at the deficient one

Question 36

draw the bonding in the following NH4+ H3O+ NH3 + BF3 CO

Answer 36

check against notes

Question 37

state 2 properties of covalent compounds

Answer 37

low melting points don't conduct

Question 38

explain why covalent compounds have low melting points and don't conduct

Answer 38

low melting points: strong covalent bonds between atoms themselves but weak intermolecular forces don't require a lot of energy to overcome don't conduct: no free electrons

Question 39

give an example of a simple molecular crystal structure. draw a diagram to show how they're soft and break easily

Answer 39

iodine diagram must name vdw IMF, check against notes

Question 40

describe the structure of a macromolecular compound

Answer 40

a giant covalent lattice with very strong covalent bonds throughout

Question 41

name the 3 examples of macromolecular compounds

Answer 41

diamond graphite graphene (1 layer of graphite)

Question 42

describe the structure of diamond

Answer 42

each carbon atom is covalently bonded to 4 others in a repeating tetrahedral pattern

Question 43

describe and explain the properties of diamond

Answer 43

high melting and boiling points, hard many strong covalent bonds require a lot of energy to overcome

Question 44

describe the structure of graphite

Answer 44

a layered structure where each carbon atom is covalently bonded to 3 others, leaving one free delocalised electron per carbon atom. weak forces between the layers

Question 45

describe and explain the properties of graphite, (and by extension where applicable, graphene)

Answer 45

can conduct electricity as the one free delocalised electron per carbon atom is free to move and carry charge throughout the structure graphite is used in lubricant as the weak intermolecular forces allow the layers to slide over one another

Question 46

define metallic bonding

Answer 46

a regular arrangement of positive metal ions surrounded by a sea of delocalised electrons

Question 47

which 2 factors can affect the strength of a metallic bond, and what are they known as collectively?

Answer 47

- atomic radius - magnitude of charge known as surface charge density collectively

Question 48

state and explain the 4 properties of metallic bonding

Answer 48

1) conducts electricity: delocalised electrons are free to move and carry charge throughout the structure 2) conduct heat: vibration of positive ions 3) high melting and boiling points: the strong forces of electrostatic attraction between oppositely charged ions require a lot of energy to overcome 4) malleable and ductile: the regular arrangement of ions allows them to slide over one another