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Chemistry Y12 > Atomic Structure > Flashcards

Atomic Structure Flashcards

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1
Q

What’s re the subatomic particles in an atoms relative mass and relative charge?

A

Proton - RM = 1 RC= +1

Neutron - Rm = 1 RC = 0

Electron - Rm - neglible (1/2000) RC = -1

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2
Q

What is the atomic number?
What is the mass number?

A

Atomic number - n of protons and the number of electrons
Mass number - n of protons and neutrons

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3
Q

What are isotopes?

A

Isotopes are atoms of the same element. They contain the same number of protons but a different amount of neutrons.

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4
Q

Isotopes have the same…. But different …?

A

Same chemical properties as they have the same number of electrons (same electron configuration)
Different physical properties e.g densities

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5
Q

What are ions?
What are polyatomic ions?

A
  • ions are charged particles
  • polyatomic atoms are made from more than 1 atom
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6
Q

Ions that have gained electrons..?
Ions that have lost electrons..?

A

negatively charged
positively charged

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7
Q

Give examples of some polyatomic ions?

A

ammonium ion = NH4+
hydroxide ion = OH-
Carbonate ion = CO3^2-
sulphate ion = SO4^2-
nitrate ion = NO3-
phosphate ion = PO4^3-

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8
Q

How do we write the formulae of ionic compounds?

A

always write the positive charge first, then negative and then we simplify.

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9
Q

What is meant by mass is conserved?

A

Total mass of reactants = total mass of products

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10
Q

What is mass spectrometry?

A

A machine that is used to measure the abundance and mass of each element allowing us to find its RAM and find the relative molecular mass of substances made of molecules

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11
Q

What happens in stage 1 of mass spectrometry?

A

IONISATION - the sample is ionised/ turned into an ion

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12
Q

2 ways a sample can be ionised

A

Electron impact, electron spray

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13
Q

Explain how ionisation happens by electron impact?

A
  • sample is vaporised
  • high energy electrons are fired at a sample from an electron gun
  • which is a hot wire filament with current flowing through it, that emits electrons
  • electrons are knocked off forming a 1+ ion
  • the 1+ ion is attracted to a negative electric plate where they are accelerated
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14
Q

Write an equation for ionisation (1+) using x ?

A

X (g) + e- —> X.+ (g) + 2e-

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15
Q

This technique is used for elements with…

A

low formula mass

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16
Q

Explain how ionisation happens by electron spray?

A
  • sample is dissolved in a volatile solvent (water/ethanol) and injected through a fine hypodermic needle to give a fine mist (aerosol
  • tip of the needle is attached to the positive end terminal of a high-voltage power supple
  • particles are ionised by gaining a proton (H+) from the solvent
  • as they leave the needle they produce XH+ ions
  • the solvent evaporated away while the XH+ ions are attracted to a negative plate where they are accelerated
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17
Q

What are XH+ ions?

A

Ions with a single positive charge and a mass of Mr+1

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18
Q

Write an equation for this type of ionisation (electron spray) using x?

A

X(g) + H ——> XH+ (g)

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19
Q

This technique is used for substances with a….

A

Higher molecular mass

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20
Q

which method is most likely to lead the break up of ions into fragments?

A

electron impact

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21
Q

What happens in stage 2 in the mass spectrometer?

A

ACCELERATION - positive ions are accelerated by an electric field so they all have the same kinetic energy

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22
Q

What equation do we use here and give it in the rearranged formula?

A

KE = 0.5 x mass x ( v^2)

Rearranged:

V = square root 2KE/ m

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23
Q

Lighter particles have a… velocity so heavier particles have a…?

A

Faster
Slower

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24
Q

What happens in stage 3 flight tube?

A

Time of flight
The positive ions travel through a hole in the negatively charged plate into a tube (ions are separated, lighter ions reach first then heavier)

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25
Q

Explain what time of flight depends on?

A

It’s velocity which in turns is it’s mass

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26
Q

What equation of time of flight calculated with?

A

T = d/v and kinetic energy equation

T = d square root m/2KE

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27
Q

This shows that time of flight is …

A

Directly proportional to the square root of m

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28
Q

Therefore lighter particles reach the detector…?

A

Faster than heavier particles

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29
Q

Explain what happens in stage 4 of mass spectrometry?

A

ION DETECTION

  • positive ions are discharged by gaining electrons from the negatively charged electric detectorplate
  • this generates a movement of electrons hence an electric current is measured
30
Q

What does the size of the current tell us?

A

The number of ions hitting the plate

31
Q

What happens in stage 5 of flight spectrometry?

A

DATA ANALYSIS
- the computer uses the data to produce a mass spectrum graph

32
Q

What does the mass spectrum show?

A
  • shows the mass to charge (m/z) ratio and abundance of each ion that reaches the detector
33
Q

The (m/z) ratio is effectively the…?

A

Mass of each ion

34
Q

What equation can we use to calculate the RAM of an element?

A

Ram formula = combined mass of all isotopes/ combined abundance of all isotopes

35
Q

For molecules ionised by electron impact the signal with the greatest m/z value is…?

A

From the molecular ion and give the relative atomic mass

36
Q

What is the definition for the relative atomic mass?

A

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

37
Q

Do Mass spectrum calculations + Time of flight and Relative atomic mass questions

A
38
Q

How do we calculate the mass of an ion?

A

the relative mass of an ion divided by Avogadro’s constant gives the mass in grams. then divide by 1000 to get kg

39
Q

How to calculate the distance of an ion in the flight tube?

A

step 1 - calculate the mass
step 2 - calculate the velocity using equation V = √2KE/m
step 3 - calculate the distance - V = d/t

40
Q

How to calculate the time of flight of an ion in the flight tube?

A

step 1 - calculate the mass
step 2 - calculate the velocity
step 3 - calculate the time

41
Q

Harder time of flight questions where we are given two isotopes, what equation would we need to use?

A

M1 = m2 equation - draw how these equations can be rearranged

42
Q

How many electrons can s orbitals hold?

A

2

43
Q

How many electrons can p orbitals hold?
What type of shape do they form?

A
  • 6
  • ## dumbbell
44
Q

How many electrons can d orbitals hold?
What type of shape do they form

A
  • 10
  • 4 leaf clover/ 4 dumbbells
45
Q

How many electrons can f orbitals hold?

A

14

46
Q

What is the aufbau principle?

A

States that the lowest energy sun- levels are occupied first

47
Q

Who developed the aufbau principle?

A

Niels bohr - said that 4s sun level is lower in energy so that one fills first

48
Q

Order of filling?

A

Draw diagram

49
Q

Describe the electron configuration of ions?

A

They loose the energy last lowest energy level
Transition metals loose 4s electrons before 3d electrons as it’s a lower energy level

50
Q

What is the ionisation energy?

A

The energy change/enthalpy change when an electron is removed from a gaseous atom.

51
Q

What is the first , second and third ionisation energy for x?

A

X

52
Q

Why is the 1st ionisation energy lower than the 2nd ionisation energy?

A
  • Because a positive ion attracts the outer electron more strongly than the neutral atom.
  • A positive ion has a smaller radius
53
Q

Explain why there is a much greater change in ionisation energy?

A
  • Electron is removed from a different energy level which is much closer to the nucleus
  • Is shielded less
  • The positive ion has a smaller radius
54
Q

Explain why down a group ionisation energy decreases?

A

As the atomic radii increases and there are more filled energy levels so there is similar shielding

55
Q

Explain why generally across a period ionoisation energy increases?

A

Due to a greater nuclear charge and there is similar shielding

56
Q

Explain why the 1st ionisation energy of group 3 (Aluminium) is less than the 1st ionisation energy of group 2 (magnesium)?

A

Al’s outer electron is in a higher energy 3p orbital whereas Mg’s outer electron is in a 3s orbital

57
Q

Explain why the 1st ionisation energy of group 6 (e.g sulphur) is less than the ionisation energy of group 5 (phosphorus)?

A

S has a pair of electrons in the same p orbital which repel

58
Q

What is a mole?

A

6.0223 x 10^23 particles
This is avogadros constant/ number

59
Q

How do we calculate Moles?

A

Moles = mass/ mr

60
Q

What is molarity?

A

Concentration- how many moles are dissolved per 1dm^3 of solution

61
Q

What is the equation for molarity/ concentration?

A

Concentration (mol dm^-3) = moles/ volume (dm^3)

62
Q

Ideal gas equation?

A

Pressure(Pa) x volume(m^3) = moles x gas constant(8.31) x temperature(k)

63
Q

What is Theoretical Yield?

A

Mass of the product that can be formed

64
Q

How to calculate the percentage yield?

A

% yield = actual yield/ theoretical yield x 100

65
Q

Why in reality the mass of a product will be less than the theoretical yield?

A
  • Sometimes not all of the reactants will react fully
  • Some of the product might have been lost (Left on filter paper, Split between transfers between containers)
  • Reversible reaction
66
Q

What is Atom economy a measure of?

A
  • A measure of how efficient a chemical reaction is
  • A measure of the proportion of reactant atoms that become part of the desired product (rather than by-product) in the balanced chemical equation
67
Q

How to calculate atom economy?

A

% atom economy = mass of desired products/ total mass of reactants x 100

68
Q

What is Water of crystallisation?

A

When a salt is formed by crystallisation from an aqueous solution, water molecules are incorporated into the structure.

Therefore the number of water molecules incorporated into a hydrated salt can be determined experimentally.

69
Q

Describe how Water of Crystallisation can be carried out?

A
  1. Measure the mass of the hydrated salt
  2. Heat the salt until all the water has been removed
  3. Calculate the mass of water removed
  4. Calculate the mass of anhydrous salt
  5. Calculate the moles of Anhydrous salt
  6. Calculate the moles of water
  7. Divide the answers from part 6 + 7 by the smallest value
70
Q

DONEEE!!

A

Chemistry Y12 (11 decks)

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