C2 atoms, elements and compounds

Question 1

define element

Answer 1

• chemical substance
• cant be broken down into simpler substances
• composed of one type of atom only

Question 2

define compounds

Answer 2

• substance made of 2 or more elements
• chemically bonded together

Question 3

define mixture

Answer 3

• 2 or more chemical substances found together
• not chemically bonded

Question 4

describe the structure of an atom

Answer 4

• central nucleus (containing neutrons and protons)
• surrounded by electrons in shells

Question 5

relative charge of a proton

Answer 5

+1

Question 6

relative mass of a proton

Answer 6

1

Question 7

relative mass of a neutron

Answer 7

1

Question 8

relative charge of a neutron

Answer 8

0

Question 9

relative mass of an electron

Answer 9

negligible

Question 10

relative charge of an electron

Answer 10

-1

Question 11

define proton number

Answer 11

number of protons in nucleus of an atom

Question 12

another word for proton number

Answer 12

atomic number

Question 13

define mass number

Answer 13

total number of protons and neutrons in nucleus of an atom

Question 14

another word for mass number

Answer 14

nucleon number

Question 15

max number of electrons in innermost shell

Answer 15

2

Question 16

max number of electrons in shells (except innermost)

Answer 16

8

Question 17

what are elements in group VIII known as

Answer 17

noble gases

Question 18

electrons in outer shell of group VIII?

Answer 18

full

Question 19

correlation between group number and number of outer shell electrons

Answer 19

they are equal

Question 20

correlation between occupied electron shells and period number

Answer 20

equal

Question 21

define isotopes

Answer 21

• different atoms of same element
• same number of protons but different numbers of neutrons

Question 22

why do isotopes of the same element have the same chemical properties

Answer 22

• same number of electrons
• therefore same electronic configuration

Question 23

what is the force which occurs in a chemical bond

Answer 23

electrostatic force

Question 24

why does chemical bonding occur

Answer 24

so all atoms involved achieve an electronic configuration with a full valence shell, which is highly stable

Question 25

what is a cation

Answer 25

positive ion

Question 26

what is an ion

Answer 26

- electrically charged particle - formed when atom loses/gains electrons

Question 27

what is an anion

Answer 27

a negative ion

Question 28

what is an ionic bond

Answer 28

- strong electrostatic attraction - between oppositely charged ions

Question 29

properties of ionic compounds:

Answer 29

- high melting/boiling point - good electrical conductor when aqueous/molten - poor electrical conductor when solid - generally soluble in water

Question 30

what is the structure of ionic compounds

Answer 30

giant lattice structure - regular arrangement - alternating positive and negative ions

Question 31

why does an ionic compound form a lattice structure

Answer 31

- electrostatic forces of attraction between alternating oppositely charged ions - act in all directions - to make giant 3d lattice

Question 32

why is the melting/boiling point of ionic compounds high

Answer 32

- strong electrostatic force of attraction in all directions - more thermal energy required to break bonds and turn substance to liquid

Question 33

how does charge on ion impact melting point of ionic compound

Answer 33

higher charge on ions, higher the melting point

Question 34

why cant ionic compounds conduct electricity while solid

Answer 34

- ions in giant 3d lattice unable to move freely - because held tg by strong electrostatic forces of attraction - ions are unable to carry charge

Question 35

why can ionic compounds conduct electricity while molten/aqueous

Answer 35

- ions are able to move - carry a charge

Question 36

how is a covalent bond formed

Answer 36

- pair of electrons is shared between 2 atoms - leading to noble gas electronic configurations

Question 37

properties of simple molecular compounds

Answer 37

- low melting/boiling points - poor electrical conductivity

Question 38

why do simple molecular compounds have low melting/boiling points

Answer 38

- intermolecular forces between molecules weak - not much energy needed to overcome

Question 39

relationship between mass of molecules and boiling/melting point

Answer 39

- larger molecules have greater number of weak intermolecular forces - therefore require more energy to separate molecules - therefore melting/boiling point higher

Question 40

why are simple molecular compounds poor electrical conductors

Answer 40

- do not have any charged particles which can move through structure - therefore charge does not flow

Question 41

what is the structure of diamond

Answer 41

- each carbon atoms shares 1 electron with 4 other carbon atoms - to make giant repeating network of covalently bonded carbon atoms

Question 42

uses of diamond and why

Answer 42

- cutting tools - extremely hard substance

Question 43

why is diamond so hard

Answer 43

made up of many strong covalent bonds in a giant structure

Question 44

what is the structure of graphite

Answer 44

- comprised of layers - each layer made up of carbon atoms, each bonded to 3 other atoms - delocalised electrons can move freely across layers - stacks of layers held tg by many weak intermolecular forces

Question 45

define allotrope

Answer 45

alternative forms of an elemental substance

Question 46

uses of graphite and why

Answer 46

- lubricant (layers can slide over each other) - electrode (good conductor of electricity)

Question 47

why can the layers in graphite slide over each other

Answer 47

- layers have weak intermolecular forces holding tg - forces are weak

Question 48

why is graphite a good conductor of electricity

Answer 48

- has delocalised electrons - which can move freely throughout structure and carry electric current

Question 49

describe metallic bonding

Answer 49

- electrostatic attraction - between positive ions in giant metallic lattice and sea of delocalised electrons

Question 50

properties of metals

Answer 50

- good electrical conductivity - malleable - high melting/boiling point

Question 51

why do metals have high melting/boiling point

Answer 51

- metallic lattice held tg by strong electrostatic forces of attraction - a lot of energy needed to separate metal atoms

Question 52

why are metals good electrical conductors

Answer 52

- delocalised electrons in metallic lattice - free to move throughout structure

Question 53

why are metals malleable

Answer 53

- regular layers, practically identical (all ions same size and distance) - when force applied, layers are able to slide past other layers

Question 54

why will aluminium have a higher conductivity than sodium

Answer 54

- one aluminium atom delocalises 3 electrons in metallic bonding - compared to only 1 in sodium - more delocalised electrons = higher conductivity