Science Chemistry Unit 1 Year12

Question 1

Define electronegativity

Answer 1

the measure of the tendency of an atom to attract a bonding pair of electrons

Question 2

State and explain trends in electronegativity

Answer 2

increases as you go across a period , neutron charge increases which attracts bonding pairs of electron more strongly
decreases as you go down a group , bonding pair of electrons is more distant to the attraction of the nucleus

Question 3

Define and explain non-polar bonds

Answer 3

atoms that have equal electronegativities , covalent bonds in diatomic molecules (H2 , CL2)

Question 4

Define diatomic molecules

Answer 4

molecules composed of only two atoms

Question 5

Define and explain polar bonds

Answer 5

bonding electrons that are pulled towards to the most electronegative atom , covalent bonds between two atoms of different electronegativities

Question 6

Define and explain 1st Ionisation Energy

Answer 6

energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms , general increase as you go across a period , increasing attraction of outer shell to nucleus because of more protons

Question 7

Define and explain 2nd Ionisation Energy

Answer 7

removing a second electron , higher than 1st as now removing an electron form a positive ion and not an atom

Question 8

Define and explain Electron affinity

Answer 8

atoms ability to gain an electron and becomes a negative ion , first electron affinity is negative , negative sign shows energy is released

Question 9

What is the most reactive element and least reactive element?

Answer 9

potassium is the most reactive , platinum is the least reactive

Question 10

What are the trends in reactivity series

Answer 10

across a period reactivity decreases

down a group reactivity increases

Question 11

What is Aufbau’s principle?

Answer 11

electrons fill lower energy orbitals before filling higher energy orbitals

Question 12

What is Bohr’s theory?

Answer 12

electrons orbit nucleus in orbitals that have a set size and energy which is related to the size

Question 13

Define ionic bonding

Answer 13

electrostatic attraction between two positively charged ions

Question 14

Explain the properties of ionic structure?

Answer 14

due to the ionic bonds they have high melting/boiling points
most ionic compounds are soluble in water
they conduct electricity in water as ions are freely to move around but not as a solid

Question 15

How do you increase the electrostatic bonds in ionic bonding?

Answer 15

Increasing the ionic charge

Question 16

What is a giant ionic lattice?

Answer 16

lattice of many ions being held together by electrostatic bonds

Question 17

Define covalent bonding

Answer 17

when two non metal atoms share an electron pairs with strong electrostatic attraction between nuclei and electrons

Question 18

Explain the properties of covalent structure

Answer 18

most have low melting/boiling points

many covalent bonds are not soluble in water and cannot conduct electricity in the water

Question 19

What is a giant covalent structure and examples

Answer 19

a lattice of many atoms bonded together e.g., diamond, graphite

Question 20

What is a tetrahedral structure?

Answer 20

a central atom, surrounded by 4 other atoms with a 109.5 degrees bond angle

Question 21

Define metallic bonding

Answer 21

the electrostatic attraction between positive metal ions and delocalised electrons

Question 22

How are delocalised electrons formed?

Answer 22

the loss and free movement of the outer shell electrons from the metal atoms

Question 23

What is a giant metallic structure

Answer 23

it is a lattice made of many atoms held together in layers by metallic bonding

Question 24

Explain the properties of metallic bonding structure

Answer 24

they have relatively high melting/boiling points, they are able to conduct heat and electricity as delocalised electrons can move around, they are insoluble in water

Question 25

Define van der Waals forces

Answer 25

a intermolecular forces that involve dipole attraction between molecules

Question 26

How do you calculate protons, electrons and neutrons from a element?

Answer 26

number of protons = atomic number number of electrons = atomic number number of neutrons = mass number - atomic number

Question 27

Define malleable and ductility

Answer 27

``` malleable = physical property of a metal to be hammered into another shape ductility = capability of a material to deform permanently ```

Question 28

How strong is hydrogen bond compared to dipole-dipole attraction and covalent bond?

Answer 28

stronger than dipole-dipole, weaker than covalent bonds

Question 29

Explain hydrogen bonding?

Answer 29

when a hydrogen atom is located between a pair of other atoms having a high electron affinity

Question 30

What is the equation for relative atomic mass

Answer 30

total mass of atoms divided by total number of atoms (regarding abundance)

Question 31

What is the equation for moles

Answer 31

moles = mass divided by mr

Question 32

What is Avogadro's constant?

Answer 32

6.02 x 10^23

Question 33

What is the equation for percentage yield?

Answer 33

actual yield ---------------------- x 100 theoretical yield

Question 34

What happens to ionisation energy as you go down a group and across a period?

Answer 34

ionisation energy decreases down a group and there is a general increase across a period except for group 3/6

Question 35

What happens to the atomic radius across a period and down a group?

Answer 35

atomic radius decreases across a period, increases down a group

Question 36

What happens to ionic radius across a period and down a group

Answer 36

ionic radius decreases along a period and increases down a group

Question 37

Name the 3 intermolecular forces from weakest to strongest

Answer 37

Van der Waals, dipole-dipole, hydrogen bonding

Question 38

State examples of polar molecules

Answer 38

water, ammonia, ethanol, sulphur dioxide

Question 39

State examples of non-polar molecules

Answer 39

carbon dioxide, noble gases, methane, most organic molecules, oxygen