Atoms, Molecules and Stoichiometry

Question 1

Define relative atomic mass

Answer 1

It is the average weighted mass of one atom relative to one atom of 12C which has a mass of exactly 12 units

Question 2

Define relative isotopic mass

Answer 2

The mass of one atom of the isotope relative relative to that one atom of 12C which has a mass of exactly 12 units

Question 3

Define relative formula mass

Answer 3

Mass of one formula unit of a compound compared with 12C where one atom of 12C has mass of exactly 12 units

Question 3

Define relative formula mass

Answer 3

Mass of one formula unit of a compound compared with 12C where one atom of 12C has mass of exactly 12 units

Question 4

Define relative molecular mass

Answer 4

Mass of a molecule compared with one atom of 12C which has a mass of exactly 12 units

Question 5

Define the mole in terms of Avogadros Constant

Answer 5

A mole of atoms is a quantity that contains Avogadros number 6.02x10^23 atoms

Question 6

State the formula for the mass of an element

Answer 6

Mass of an element = AR of the element /Mr of compound x mass of compound

Question 7

State the formula linking concentration in g/dm^3, mold 3 and Mr

Answer 7

Concentration in g/dm3 =concentration in mold/dm3x Mr

Question 8

Define the empirical formula

Answer 8

If a compound shows the simplest whole number ratio of elements in the compound

Question 9

Define the molecular formula

Answer 9

Shows the real numbers of each element in a molecule of a compound

Question 10

State the formula used in calculating volumes of gases in the burning of hydrocarbons

Answer 10

CxHy (g) + ( x + y/4) O2 (g) _______ xCO2 (g) + y/2 H20(l)

Question 11

What is the behavior of particles when they enter an electric field

Answer 11

Protons are attracted to the negative plate
Electrons are attracted to the positive plate
Neutrons remain straight as they have no charge

Question 12

What causes deflection of the beams of particles

Answer 12

Deflection depends on whether the beams of particles enter the electric field with the various particles having the same speed or same energies

Question 13

Describe how the beam of particles behave if they have the same speed

Answer 13

Protons are deflected on a curved path toward the negative plate
Electrons are deflected on a curved path towards the positive plate
Neutrons are not deflected as they have no charge

If the Electrons and Protons are travelling with the same speed Electrons are deflected more because their more lighter as compared to the heavier protons

Question 14

Describe how the beam of particles behave if they have the same energies

Answer 14

Protons are deflected on a curved path towards the negative plate
Electrons are deflected on a curved path toward the positive plate
Neutrons are not deflected
The amount of deflection is exactly the same in the electron beam as the proton beam if the energies are the same but in opposite directions

Question 15

What does isoelectronic mean

Answer 15

Atoms with the same number of Electrons

Question 16

What does isotonic mean

Answer 16

An atom with the same number of Neutrons

Question 17

What does isotopic mean

Answer 17

An atom with the same number of protons

Question 18

Isotopes have the same number of

Answer 18

Protons and Electrons
Electronic configuration
Same chemical properties

Question 19

Isotopes of different

Answer 19

Nucleon number
Densities
Masses
Molecular speed

Question 20

The formular to calculate number of Electrons in an energy levels

Answer 20

2n^2

Where n is the quantum number

Question 21

As we move away from the nucleus…. Does the energy of Electrons increases or decrease

Answer 21

It increases

Question 22

When arranging Electrons… Which energy level will be filled first

Answer 22

Electrons will always fill the inner level with low energy level then moves to the outer shell with high energy level

Question 23

The energy of electrons in the sub-shells increases in the order

Answer 23

s < p < d < f

Question 24

What is the order in which energy levels are filled

Answer 24

1s, 2s, 2p,3s, 3p, 4s,3d,4p,4d

Question 25

Describe the shape of the s orbital

Answer 25

It is spherical and non directional

Sizes increases as energy level increases

Question 26

Describe the shape of the p orbital

Answer 26

It is shaped like a dumb bell
It is directional
The lobes get longer as we increase in energy levels

Question 27

What is an orbital

Answer 27

Space you likely to meet an electron

Question 28

Define ionization energy

Answer 28

Ionization energy is the energy needed to remove an electron from a mole of atoms of an element in their gaseous state

Question 29

What are the factors affecting ionization energies

Answer 29

1. Nuclear Charge
2. Shielding effect
3. Atomic radii

Question 30

Describe the trends of ionization energy across the period

Answer 30

Ionization energy across a period increases since nuclear charge increases and shielding effect remains constant
Therefore force holding valence Electrons becomes stronger
Shell number remains the same, Proton number increases and Atomic radii decreases

Question 31

Describe the trends of ionization energy down a group

Answer 31

Ionization energy down a group falls
New shells added decrease
Attraction of nucleus to valence elctrobs decreases
Shielding effect increases

Question 32

Explain how + nuclear charge affects ionization energy

Answer 32

The greater the number of protons in the nucleus the greater the amount of positive charge
The greater the + charge the greater the attraction force between the nucleus and outer Electrons
More energy is needed to overcome this force hence ionization energy is higher

Question 33

Explain how size of atom/ion (nucleus and outer Electrons) affects ionization energy

Answer 33

The larger the size of the atom the greater the distance between the nucleus and outer electrons
The greater the distance between the nucleus and outer electron the weaker the force of attraction between the nucleus and outer electron
The outer electrons experience >shielding effect from the inner Electrons
Less energy is need to over come the attraction so IE is low

Question 34

Explain how shielding effect affects ionization energy

Answer 34

The greater the shielding effect, the weaker the attractive force between the nucleus and outer electrons
Less energy is required to overcome the attractive So, the ionisation energy is lower.
– The greater the shielding effect, the lower the ionisation energy

Question 35

What is the shielding effect

Answer 35

All electrons are negatively-charged, so they repel each Electrons in full inner shells will repel the outer electrons and so prevent the full nuclear charge being felt by the outer electrons. This is called shielding or screening

Question 36

When there is a big jump

Answer 36

It shows that we are now moving into an energy level closer to the nucleus
The number of Electrons before the big jump shows the group number of electrons

Question 37

There is a drop from Group 2 to 3 because

Answer 37

It is easier to remove energy from a higher energy p orbital hence there is a drop in ionisation energy

Question 38

There is a drop from Group 5 to 6 because

Answer 38

Electrons from Group 5 are singly filled and are more stable compared to the Group 6 electrons pairing which results in increased repulsion
Less energy is needed to remove elctrons in group 6