Atomic Structure

Question 1

Mass Number

Answer 1

Number of protons/electrons

Question 2

Atomic Number

Answer 2

Number of protons

Question 3

Proton

Answer 3

• Charge: +1
• Mass: 1

Question 4

Neutron

Answer 4

• Charge: 0
• Relative Mass: 1

Question 5

Electron

Answer 5

• Charge: -1
• Mass: 1/1836

Question 6

Isotopes

Answer 6

Atoms of an element with the same number of protons but a different number of electrons

Question 7

Structure of the Atom

Answer 7

• Mostly empty space
• Small nucleus in the centre
• Nucleus is made up of protons and neutrons, is positively charged and has a radius of 1x10^-14

Question 8

Relative Atomic Mass

Answer 8

Total mass of atoms/Total number of atoms

Question 9

Robert Boyle

Answer 9

• 1662
• Proposed there were some substances that couldn’t be made simpler

Question 10

John Dalton

Answer 10

• 1803
• Suggested elements were made of invisible atoms that can’t be broken down

Question 11

Henri Becquerel

Answer 11

• 1896
• Discovered radioactivity showing that particles could come from inside the atom (decay)

Question 12

JJ Thompson

Answer 12

• 1897
• Discovered the electron
• Proposed the plum pudding model

Question 13

Ernest Rutherford

Answer 13

• 1911
• Suggested the atom was mostly empty space with a dense nucleus containing the positive charge
• Suggested the nuclear model
• Discovered the proton

Question 14

Geiger and Marsden

Answer 14

• 1908-1913
• Conducted the gold foil experiment which showed the atom was mostly empty space

Question 15

Niels Bohr

Answer 15

• 1913
• Suggested electrons orbit the nucleus in shells that are at regular distances from the nucleus

Question 16

James Chadwick

Answer 16

• 1932
• Discovered the neutron

Question 17

Mass Spectrometry

Answer 17

Used to determine the elemental and isotopic composition of a sample

Question 18

Electrospray Ionisation

Answer 18

• The sample is dissolved in a volatile solution
• The solution is forced through a fine hollow needle connected to the positive terminal of a power supply
• This produces tiny positively charged droplets which have lost electrons to the positive charge supply

Question 19

Electron Impact Ionisation

Answer 19

• The sample is vapourised and high energy electrons are fired at it using an electron gun
• This knocks off an electron from the sample forming a 1+ ion

Question 20

Mass Spectrometry: Ionisation

Answer 20

• All the different isotopes of an element are placed in a sample chamber
• Atoms are all ionised and converted to positive ions

Question 21

Mass Spectrometry: Acceleration

Answer 21

• Positively charged ions become attracted to a negatively charged plate
• This causes the ions to accelerate which increases the kinetic energy of the ions
• Ions with the same charge have the same kinetic energy

Question 22

Mass Spectrometry: Ionic Drift

Answer 22

• When the ions pass through the plate they stop accelerating and drift down the chamber toward the detector
• Lighter ions move faster towards the detector than heavier ions
• As a result they reach the detector first

Question 23

Mass Spectrometry: Detection

Answer 23

• The positive ions gain electrons at the detector
• Electron transfer causes current to flow

Question 24

Why is the interior of a mass spectrometer a vacuum?

Answer 24

To prevent ions from colliding with molecules in the air

Question 25

How can you tell the Mass of an Isotope?

Answer 25

Finding out the time it took for the ions of a sample to reach the detector

Question 26

How can you tell the abundance of an Isotope?

Answer 26

• Find out the size of the current produced when each isotope hits the detector
• A more abundant isotope produces a greater current

Question 27

Mass Equation

Answer 27

(Ar/1000) x moles (Avogadro’s Constant)