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AS physical chemistry > Chapter 1 - Atomic structure > Flashcards

Chapter 1 - Atomic structure Flashcards

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1
Q

what is atomic number

A

The number of protons in the nucleus and is referred to using the letter Z

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2
Q

what is the mass number

A

the total number of protons and neutrons in the nucleus and also refered to using the letter A

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3
Q

what is relative atomic mass

A

the mean mass of an element divided by 1/12 of the mass of a carbon 12 atom

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4
Q

What are isotopes

A
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5
Q

examples of isotopes of carbon

A
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6
Q

how has the atomic structure changed (image)

A
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7
Q

how many electrons are in each shell up to the third shell

A

1st shell - 2
2nd shell - 8
3rd shell - 18
2n^2

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8
Q

what is an ion

A

ions are formed when an atom gains or loses electrons meaning it is no longer neutral and will have an overall charge

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9
Q

what is mass spectrometry

A

an analytical technique used to identify different isotopes of an element and to find the overall relative atomic mass of an element

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10
Q

what is the formula for realative atomic mass

A

average mass of one atom / 1/12 of a carbon 12 atom

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11
Q

what is time of flight mass spectrometry

A

it is a form of mass spectrometry used to record the time it takes for ions of each isotope to reach a detector. This creates a spectra showing each type of isotope present

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12
Q

what are the 4 main steps in TOF mass spectrometry

A
  1. Ionisation
  2. acceleration
  3. Ion drift
  4. detection
    (alanysis)
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13
Q

what are the conditions for TOF mass specrometry

A

the entire apparatus must be in a vacuum to particles from colliding with air particles

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14
Q

what is electrospray ionisation with the equation

A

when the sample is dissolved in a volatile solvent and forced through a fine hollow needle which is connected to the positive termial of a power supply. When the sample leaves the needle it produces small positively charged droplets that have gained a proton from the solvent.

X(g) + H+ –> XH+ (g)

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15
Q

what is electron impact/ electron bombardment with the equation

A

the sample is vaporised and high energy electrons are fired at it from an electron gun (hot wire filament) with a current running through it that emits high energy electrons

X (g) + e- –> X+ (g) + 2e-

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16
Q

what is acceleration

A

The positive ions are attracted a negatively charged plate and accelerate towards it as they all move wwith the same acceleration and with difference speed. lighter ions and more highly charged ions move faster.

17
Q

what is ion drift

A

the ions pass through a hole in the negatively charged plate forming a beam of ions towards the detector.

18
Q

what is detection

A

when ions with the same charge arrive at the detector the lighter ions reach the end first as they have higher velocities. The flight times are recorded. The positive ions pick up an electron from the detector, which causes a current to flow

19
Q

What is data analysis

A

The signals from the spectrometer are passed to a computer which generate a mass spectrum

20
Q

labelled picture of mass spectrometer

A
21
Q

example of a mass spectrum or chlorine

A
22
Q

what is the m/z value

A

the mass to charge ratio

23
Q

If there an ion is 2+ instead of 1+ what is the effect on the m/z value

A

it will half as the ion will move twice as fast

24
Q

what are subshells

A

They are divisions of the main shells and are groups of electrons.
the 4 subshells are s, p, d, f

25
Q

what are orbitals

A

the space in which an electron is most likely to be found. each orbital contains 2 electrons

26
Q

how many electrons are in each subshell

A
27
Q

graph showing the energy levels of all the orbitals

A

4s has a lower energy than 3d

28
Q

what is the spin property of an electron

A

Two electrons in the same orbital must have opposite spins
This is represented by arrows facing in opposite directions

29
Q

What are the rules in allocating electrons to orbitals

A
30
Q

what are the exceptions to allocating electrons to their orbitals

A

if a subshell has one electron in each orbital however has tow electrons in one of them it will move to the orbital of a higher energy. e.g. 3p3 4s1 instead of 3s4

31
Q

what is ionisation energy

A

ionisation energy is the energy to remove one mole of electrons from one mole of atoms in their gaseous. KJmol-1

32
Q

what is the difference between the first ionisation energy and the second and third.

A
33
Q

what are successive ionisation energies

A

when the multiple ionisation energies are followed one after the other

34
Q

what are the equations for ionisation energies in sodium

A
35
Q

what happens to the first ionisation energy as you move across a period

A

The first ionisation energy increases dues to more protons in the nucleus increasing the electrostatic forces of attraction.

36
Q

what happens to the first ionisation energy as you move down a group

A

the ionisation energy decreases as the shielding from electrons increases and the distance from the nucleus increases meaning lower electrostatic forces off attraction even though the number of protons in the nucleus increases

37
Q

why are there jumps in the successive ionisation energy graphs

A

This is due to a change in the energy level because the electron is being removed from an orbital closer to the nucleus so more energy is required.

38
Q

Why are there dips in first ionisation energies (aluminium and sulfur)

A

Aluminium - Only has one electron in the highest energy level orbital so less energy is required to move it
Sulphur - has two electrons in the same orbital with the other orbitals only having one electron each. This electron is easier to remove due to the repulsion between both electrons in this orbital

AS physical chemistry (7 decks)

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