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A-LEVEL CHEMISTRY > Atomic Structure > Flashcards

Atomic Structure Flashcards

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1
Q

Describe the development of the atom.

A

Democritus - claimed atoms couldn’t be split
John Dalton - determined atoms were tiny particles (hold spheres that couldn’t be split) which made up elements.
J.J. Thomson - Discovery of electrons and proof that could be split
Rutherford - Developed nuclear model (mass concentrated in centre and electrons in shell orbiting)
James Chadwick - Experiment showed existence of neutrons

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2
Q

Name the 3 sub-atomic particles.

A

Protons, neutrons and electrons

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3
Q

What is the relative mass and charge of a proton?

A

Relative Mass = 1

Relative Charge = +1

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4
Q

What is the relative mass and charge of an electron?

A

Relative Mass = 1/1840

Relative Charge = -1

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5
Q

What is the relative mass and charge of a neutron?

A

Relative Mass = 1

Relative Charge = 0

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6
Q

What is the mass number?

A

Number of protons and neutrons.

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7
Q

What is the atomic number?

A

The number of protons.

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8
Q

What is an isotope?

A

Atoms with the same number of protons but different number of neutrons.
The mass number is different because of the different number of neutrons

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9
Q

What is different about the reactivity of isotopes?

A

They react chemically the same because of the same electron configuration.

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10
Q

What is time of mass spectrometry?

A

Powerful instrument method of analysis.
It can be used for:
- Finding the abundance and mass of each isotope in an element allowing us to determine its relative atomic mass
-Find the relative molecular mass of substances made of molecules

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11
Q

What is a common form of mass spectrometry?

A

Time of flight spectrometry - particles of the substance are ionised to form +1 ions which are accelerated so they all have the same kinetic energy. The time to travel a fixed distance is then used to find the mass of each ion in the sample

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12
Q

What is the name of the first stage and name the two techniques?

A

Ionisation - Electron Impact & Electrospray

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13
Q

Describe electron impact.

A
  • Sample is vaporised to a gas
  • High energy electrons fired at it from an electron gun
  • Electron gun is hot wire filament with current running through it that emits electrons
  • Usually knock off one electron from each particle forming a 1+ ion.
  • 1+ ions then attracted towards a negative electric plate where they are accelerated
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14
Q

What is the electron impact used for?

A

Elements and substances with low formula mass (can be inorganic and organic)

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15
Q

Describe the electrospray ionisation.

A
  • Sample dissolved in a volatile substance
  • Injected through fine hypodermic needle giving a fine mist/ aerosol
  • Tip of needle attached to positive terminal of high voltage supply
  • Particles are ionised by gaining a proton as it leaves the needle
  • Solvent evaporates whilst ions are attracted towards negative plate where they’re accelerated
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16
Q

What is the second stage of time flight spectrometry?

A

Acceleration

17
Q

Describe acceleration

A
  • Positive ions accelerated using an electric field so that they all have the same kinetic energy
  • The velocity of each particle depends on its mass.
  • Lighter particles have faster velocity and heavier particles have a slower velocity
18
Q

What is the third stage of time flight and spectrometry and describe it?

A

Flight tube

  • Positive ions travel through a hole in the negatively charged plate into a tube.
  • ToF of each particle through this flight tube depends on its velocity which in turn depends on its mass (lighter = faster , heavier = slower)
19
Q

What is the fourth stage of time flight spectrometry and describe it?

A

Detection

  • +tive ions hit negatively charged electric plate.
  • When hitting the detector plate, positive ions are discharged by gaining electrons from the plate.
  • Generates movement of electrons hence an electric current is measured.
  • Size of the current gives a measure of the number of ions hitting the plate
20
Q

What is the mass spectrum?

A
  • A computer uses data to produce the mass spectrum.
  • It shows the mass to charge (m/z) ratio and abundance of each ion that reaches the detector.
  • m/z effectively the mass of each ion
21
Q

Why may there be peaks at lower m/z values?

A

Due to fragments caused by the break up of molecular ion

22
Q

How many electrons can fit on a s-sub-level?

A

2

23
Q

How many electrons can fit on a p-sub-level?

A

6

24
Q

How many electrons can fit on a d-sub-level?

A

10

25
Q

What is it called when an electron fills a volume in a space?

A

atomic orbital

26
Q

What are the letters of the four-sub shells?

A

S, P, D, F

27
Q

How many electrons fit on a f-sub-shell?

A

14

28
Q

How many electrons are in the 1st main energy level and what sub-shells does it have?

A

S

29
Q

Describe the spin property of electrons?

A
  • two electrons in the same orbital must have opposite spins

- electrons usually represented by arrows pointing up or down to show the directions of spin

30
Q

What are the three rules for allocating electrons to atomic orbitals?

A
  • Orbitals of lower energy filled first
  • Orbitals of the same energy fill singly before pairing begins as electrons repel each other
  • No atomic orbital can hold more
31
Q

What is ionisation energy?

A

The energy required to remove a mole of electrons from a mole of atoms in the gaseous state (measured in kJ mol -1)

32
Q

Describe successive ionisation energy.

A

1st needs least energy (1st IE)
2nd needs more energy (2nd IE)
3rd needs even more energy (3rd IE)
the fourth needs more and so on

33
Q

Describe the trend in ionisation energies down a group

A

The ionisation energy decreases down a group

34
Q

Explain the trend of ionisation energy down a group

A

Further distance between the nucleus and outer electron which means more shielding and therefore stronger force of attraction.

35
Q

Describe the trend in ionisation energies across a period

A

There’s a higher ionisation energy.

36
Q

Explain the reason for the higher ionisation energy

A

There are more protons therefore the same shielding and stronger FoA.

37
Q

Using the example of period 3, why is there a drop between Mg and Al?

A
  • new sub-shell
  • a higher energy level.
  • the same shielding
  • weaker FoA
38
Q

Why is there a drop between p and S?

A

In sulfur there is 2 electrons in the same orbital meaning the repulsion between the two makes it easier to remove one - less FoA

A-LEVEL CHEMISTRY (9 decks)

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