Chapter Two

Question 1

Leucippus stated that

Answer 1

If a piece of matter were subdivided over and over again eventually it would not be able to be divided any further

Question 2

Democritus

Answer 2

• Expanded on Leucippus’s idea and named the final piece of matter ‘atomos’
• He believed different substances had atomos of different shapes and sizes which gave substances different properties

Question 3

Atomos means

Answer 3

Indivisible

Question 4

Aristotle

Answer 4

Believed all matter was made of four elements > fire, water, air and earth

Question 5

John Dalton

Answer 5

• All matter was made up of these indivisible atoms
• Atoms had different weights
• Compounds are formed through the combination of atoms
• Atoms of a given element are identical in size and mass and when they combine to form compounds they do so only in the simplest ratio (some of these points are untrue)

Question 6

Joseph John Thomson

Answer 6

• Particles flow from the negative electrode to the positive electrode and the stream of particles is repelled by another negative electrode
• Must be negatively charged particles present in all atoms
• Because atoms are electrically neutral he proposed there must also be positive charges to balance out the negative ones
• Plum pudding model

Question 7

Plum pudding model

Answer 7

• Negatively charged particles were spread throughout the positively charged sphere of the atom like raisins in a plum pudding
• These negatively charged particles became known as electrons

Question 8

Ernest Rutherford

Answer 8

• Most of the atom must be empty space
• Most of the mass and positive charge of an atom must be located in a tiny region, the nucleus of the atom
• Electrons orbited the nucleus like planets around the sun
• Called the positive subatomic particle proton
• Believed there was a yet undiscovered neutral particle in the nucleus

Question 9

James Chadwick

Answer 9

Confirmed the neutral particle and called it the neutron

Question 10

Electrons

Answer 10

• Negatively charged particles in a cloud surrounding the nucleus
• Very little contribution to an atoms overall mass
• Negative particles attract positive particles which keeps the atom bound together

Question 11

The nucleus

Answer 11

• 99.97% of an atoms mass
• The subatomic particles inside are referred to collectively as nucleons

Question 12

Proton charge

Answer 12

+1

Question 13

Proton relative mass

Answer 13

1

Question 14

Proton mass in kg

Answer 14

1.673x10^-27

Question 15

Neutron charge

Answer 15

0

Question 16

Neutron relative mass

Answer 16

1

Question 17

Neutron mass in kg

Answer 17

1.675x10^-27

Question 18

Electron charge

Answer 18

-1

Question 19

Electron relative mass

Answer 19

1/1800

Question 20

Electron mass in kg

Answer 20

9.109x10^-31

Question 21

Atomic number

Answer 21

The number of protons in an atoms nucleus, represented by the symbol ‘Z’

Question 22

Mass number

Answer 22

• Always a whole number
• The number representing the number of protons + neutrons in the nucleus, symbol = ‘A’

Question 23

Isotopes

Answer 23

• Atoms of the same element with different numbers of neutrons and in turn mass numbers
• Identical chemical properties but different physical properties

Question 24

What causes an isotope to be unstable and radioactive

Answer 24

• A significant difference between the number of neutrons and protons
• These isotopes undergo radioactive decay, emitting various forms of radiation and turn into more stable, lighter nuclei

Question 25

What standard are the masses of individual isotopes of each element ccompared to

Answer 25

Carbon-12

Question 26

Relative atomic mass

Answer 26

The average relative mass of an atom in this naturally occurring mixture of isotopes

Question 27

Relative abundance

Answer 27

• %
• The proportion of each isotope in the sample of each element

Question 28

Equation for relative atomic mass

Answer 28

Relative atomic mass = Relative isotopic mass x Relative abundance/100
OR
Relative atomic mass = (Relative abundance x relative isotopic mass) + (relative abundance x relative isotopic mass)/100

Question 29

Relative abundance equation

Answer 29

Relative atomic mass = ( relative isotopic mass x a) + (relative isotopic mass x (100-a)) / 100

a = lighter isotope abundance
100-a = heavier isotope abundance

Question 30

Mass spectrometry

Answer 30

• A technique used to measure the mass of atoms of molecules
• Can identify the presence and relative abundance of isotopes in a sample of an element (in context of atomic structure)
• Can measure the mass of molecules which helps determine structure

Question 31

Relative isotopic mass

Answer 31

The mass of an individual isotope of each element compared to the standard of carbon-12

Question 32

Mass spectrometer

Answer 32

• Separates the individual isotopes in a sample of the element
• Determines the mass of each isotope relative to the carbon-12 standard
• Calculates the relative abundance of the isotopes in the sample

Question 33

Mass spectra

Answer 33

• The information from the mass spectrometer is presented graphically and plots the relative abundance of each ion against its mass-charge ratio (m/2)
• For most elements the proportion of its isotope is approximately the same in every sample

Question 34

Relative isotopic abundance

Answer 34

The % amount of an isotope in a natural element

Question 35

Mass spectra equation

Answer 35

% = peak height/total peak height x100

Question 36

Chemical symbol

Answer 36

One or two letters that represent the element (the first is always capitalised)