Atomic Structure

Question 1

What did Robert Boyle do?

Answer 1

He came up with the idea that matter is made up of tiny particles that cannot be subdivided and that putting these particles together made compounds.

Question 2

What did John dalton do?

Answer 2

He named the tiny particles atoms and defined them as being indivisible and indestructible. He also said that all atoms of an element are identical and have the same mass and chemical properties.

Question 3

What did Joseph John Thomson do?

Answer 3

He proposed that atoms contained electrons and proposed the plum pudding model of the atom (electrons surrounded by a cloud of positive charge)

Question 4

Who’d discovered that the mass of an atom is concentrated in a nucleus and that all the positive charge is contained within the nucleus and how?

Answer 4

Ernest Rutherford through his experiment of the deflection of alpha particles through foil.

Question 5

Who discovered protons?

Answer 5

Henry Moseley and Ernest Rutherford

Question 6

Who discovered the neutron?

Answer 6

James Chadwick

Question 7

What did Niels Bohr do?

Answer 7

Discovered that electrons orbit the nucleus in energy levels

Question 8

State the relative mass and charge of the proton, neutron and electron

Answer 8

Mass charge
Proton 1 +1
Neutron 1 0
Electron 1/1837 -1

Question 9

What are the protons and neutrons called together?

Answer 9

Nucleons

Question 10

Why dont protons in the nucleus repel each other?

Answer 10

Because a strong nuclear force acts over the small size of the nucleus and binds all the nucleons together

Question 11

What are the multipliers and meanings of:
Mega
Kilo
Deci 
Centi
Milli
Micro
Nano 
Pico

Answer 11

Prefix multiplier meaning
Mega 10▪6 1000 000
Kilo 10▪3 1000
Deci 10 ▪-1 0.1
Centi 10 ▪-2 0.01
Milli 10 ▪-3 0.001
Micro 10 ▪-6 0.000001
Nano 10 ▪-9 0.000000001
Pico 10▪-12 0.000000000001

Question 12

What is the atomic number?

Answer 12

The atomic number is the number of protons in the nucleus. It has the symbol Z and is also known as the proton number. It is also the number of electrons because protons and electrons are equal

Question 13

What is the mass number?

Answer 13

The total number of protons and neutrons in the nucleus of an atom. The electrons are so small they are insignificant

Question 14

What are isotopes?

Answer 14

Atoms of the same element with different mass numbers

Question 15

Why do isotopes all have the same chemical properties?

Answer 15

Because they have the same number and arrangement of electrons

Question 16

What different physical properties may isotopes have?

Answer 16

Their rate of diffusion (depends on mass)

Their nuclear properties such as radioactivity

Question 17

What are non radioactive isotopes called?

Answer 17

Stable isotopes

Question 18

What is the percentage of each isotope that occurs naturally on earth called?

Answer 18

The relative isotopic abundance

Question 19

What is the percentages of isotopes of elements that occur in space called?

Answer 19

Isotope signature

Question 20

What are mass spectrometers used for?

Answer 20

Identifying the mass of an element, isotope or molecule. Knowing the mass of a particle can help scientists identify the particle

Question 21

Describe the different stages of a time of flight mass spectrometer

Answer 21

1) Ionisation: the sample being tested is vaporized and injected into the spectrometer. It is bombarded by high energy electrons which knock off one or two electrons (normally just one) and positively charged ions are produced. Sometimes softer ionisation is achieved by using desorptive ionisation.
2) Acceleration: the electric field has a fixed strength as the potential difference is constant. It accelerates the ions so that all the ions with the same charge have the same kinetic energy and are travelling at the same speed.
3) Ion drift: the ions reaching the drift regions will have two variables, their mass and charge. This is described by their mass to charge ratio (m/z ratio). Heavier ions move slower and singularly charged ions move slower. The ions are in the flight path and the time taken to reach the detector is called the flight time
4) Ion detector: the ions are distinguished by different flight times at the ion detector. The electronic signal is used by computer software to produce a mass spectrum.

Question 22

The chart produced by a mass spectrometer is called a mass spectrum. Describe what it shows

Answer 22

• The m/z charge of the ion. The position of each peak shows this. This number is usually just the mass of the iron as most ions have a 1+ charge.
• the relative abundance of each isotope. The size of each peak shows this

Question 23

How do you calculate the relative atomic mass from isotopic abundance?

Answer 23

(Relative abundance x m/z charge) + this for every other isotope/ 100

Question 24

Define the relative atomic mass

Answer 24

The average mass of an atom compared with 1/12 the mass of a carbon-12 atom

Question 25

How do you work out the relative atomic mass?

Answer 25

Average mass of one atom of an element/ 1/12 the mass of one carbon-12 atom

Question 26

Define the relative molecular mass

Answer 26

Average mass of one molecule/ 1/12 the mass of one carbon-12 atom

Question 27

How do you work out relative molecular mass?

Answer 27

Average mass of one molecule/1/12 the mass of one carbon-12 atom

Question 28

Describe how electrons are arranged with specific regard to electron shells

Answer 28

• in electron shells around the nucleus
• each electron shell has a particular value
• electrons can be described as being in a particular shell
• within each shell there are a number of sub-shells (orbitals)
• the sub-shells are given the letters s, p, d and f

Question 29

How many electrons can each orbital hold?

Answer 29

Two electrons that spin in opposite directions

Question 30

How many orbitals are there in each sub-shell and what are the maximum number of electrons?

Answer 30

Sub level s p d f

Orbitals 1 3 5 7

Electrons 2 6 10 14

Question 31

What instrument splits light into its component colours?

Answer 31

A spectroscope

Question 32

What happens if electrons absorb electrical energy?

Answer 32

They get excited and move into a higher energy level. This is not a stable arrangement and the electrons fall back to their original position (ground state) in one or more steps. Ae the electron returns to the loew energy level energy is emitted as radiation. If this radiation is in the visible range you see it as coloured light. A spectrospe will split this radiation into lines of a particular colour. The energy gaps between the energy levels in the atom determine the wavelength of the radiation emitted. All the lines for an element make up its emission spectrum

Question 33

What is the electron configuration?

Answer 33

The arrangement of electrons in an atom written as symbols. It includes sub-shells as well as shells and shows the number of electrons in each. E.g. Be= 1s2,2s2

Question 34

What is a spin diagram?

Answer 34

It shows the direction of spin or all the electrons in a sub-shell.

E.g. /| |/ is one orbital

Question 35

In what order are electrons added?

Answer 35

Between hydrogen and argon electrons or increasing energy are added, one per element in sub-shell order 1s, 2s, 2p, 3s, 3p. Then for potassium the next electron skips sub-shell d and goes into 4s. This is because the 3d sub-shell has a higher energy than the 4s sub-shell.

Question 36

How do you fill electron orbitals?

Answer 36

Electrons first occupy empty orbitals and are parallel spined. When these orbitals each have one electron additional electrons are spin paired, the second electron will spin in the opposite direction

Question 37

How are abbreviated electron configurations written?

Answer 37

Using noble gas configurations. For example the abbreviated configuration for potassium in (Ar) 4s1

Question 38

What is the ionisation energy?

Answer 38

The energy required to remove an electron from an atom in it’s gaseous state

Question 39

What is the first ionisation energy?

Answer 39

The enthalpy change when one mole of gaseous atoms forms one mole of gaseous ions with a single positive charge

Question 40

What are general half equations for the first and second ionisation energies?

Answer 40

M (g) -> M+ (g) +e-

M+(g) -> M2+ (g) + e-

Question 41

What are the ionisation energy values for removing the second and subsequent electrons called?

Answer 41

The successive ionisation energies

Question 42

What are ionisation energies measured in?

Answer 42

KJ mol -1

Question 43

Why do the first ionisation energies decrease down group 2?

Answer 43

• the number of electron shells between the outer electron and the nucleus is increasing; the electron shells shield the outer electron from the attraction of the nucleus
• the radius of each atom is increasing as you go down group 2 so the distance between the outer electron and nucleus is increasing

Air this means the outer electrons are easier to remove and the first ionisation energies decrease

Question 44

Why does the first ionisation energy increase along period 3?

Answer 44

As you move along the period each element has one more electron than the last but they also have another proton and so the positive charge on the nucleus increases and the electrons are attracted more strongly. The electrons dont move down an energy level so the charges dont balance out.

Question 45

Why does the first ionisation of aluminium drop after magnesium?

Answer 45

Because the electron in aluminium starts to fill a 3p orbital and s orbitals have a higher energy level than p orbitals because they are closer to the nucleus so it is easier to remove an electron from the p orbital

Question 46

Why is there a fall in ionisation energy between phosphorus and sulfur?

Answer 46

Because sulfurs first electron enters a 3p orbital already containing one electron. These spin in opposite directions and repel each other so it takes Lee’s energy to remove the first electron from sulfur than phosphorus

Question 47

In successive ionisation energies there is a big increase in the energy required to remove the 2nd and 3rd electrons. Why is this?

Answer 47

Because the third electron is taken from the second shell which is closer to the nucleus