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Personal CHEM > 1. Atomic Structure > Flashcards

1. Atomic Structure Flashcards

1
Q

3 factors of the Bohr Model:

A
  1. protons + neutrons are found in the centre of the atom called the nucleus
  2. protons + neutrons can also be called nucleons
  3. electrons orbit around the nucleus in shells/energy levels
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2
Q

Name Fundamental Particles of an Atoms, their relatives masses and relative charges

A
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3
Q

Atomic Number is equal to what

A

equal to the number of protons

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4
Q

Mass Number is equal to what

A

equal to the sum of the number of protons and neutrons

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5
Q

What are isotopes

A

Atoms with the same number of protons but different number of neutrons

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6
Q

Why do isotopes of the same element have the same chemical properties?

A

They have the same electronic configuration

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7
Q

Isotopes have the same electron configuration so …

A

They have the same chemical properties

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8
Q

Number of Neutrons =

A

Mass Number - Atomic Number

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9
Q

Atoms have a neutral charge, why?

A

Number of protons = Number of electrons

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10
Q

What are cations?

A

An atoms that has lost electrons so protons>electrons and is now an ion

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11
Q

What are anions?

A

An atom that has gained electrons so electrons>protons and is now an ion

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12
Q

1st Ionisation Energy:

A

the amount of energy needed to remove a mole of e- from a mole of atoms, in the gaseous state (units= kJ mol-1

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13
Q

Equation for the 1st ionisation energy (of Potassium, K):

A

K(g) → K+ (g) + e-

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14
Q

1st 3 Ionisation Energies of Boron:

A

1: B(g) → B+ (g) + e-
2: B+(g) → B 2+ (g) + e-
3: B 2+(g) → B 3+ (g) + e-

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15
Q

3 factors that influence I.E:

A

1) Shielding
2) Nuclear Charge (number of protons in the nucleus)
3) Distance from nucleus

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16
Q

Trend in 1st I.Es of elements down a group:

A
  • Shielding increases
    (- Distance from nucleus increases)
  • Weaker attraction between nucleus and outermost e-
  • 1st I.E decreases down group
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17
Q

Why do I.Es 1-3 increase?

A

Each e- is being removed from a more +ve ion each time. (attraction between the electrons and the protons increase as there are less electrons being attracted by the same number of protons)

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18
Q

Why does the 4th I.E increase drastically?

A

The 4th e- being removed from a shell closer to the nucleus and a more positive ion and so is much more strongly attracted to the nucleus

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19
Q

The following data shows the first seven successive ionisation energies of a period 3 element. State which element it is and explain your reasoning.

A

(Calculate gap between each e- removed)
- Largest increase between 4th + 5th I.Es
- 5th e- is on the shell closer to the nucleus
- Element must have 4 e- on its outer shell
- Period 3, Group 4 = Silicon

20
Q

Why is Li a bigger atoms than Be?

A
  • Same shielding
  • Be has more protons
  • so, stronger attraction to the outer e-
21
Q

Why is Li a bigger atoms than He?

A
  • Li has an extra shell
  • Li’s outermost e- is further away from the nucleus
  • Outer e- is more shielded
  • Outer e- less strongly attracted to the nucleous
22
Q

Which element has the highest 1st I.e of all the elements?

A

He. Because it has same shielding as H but more protons than H.

23
Q

Trend in 1st I.E across a period:

(use example of Period 1 to explain)

A
  • General increase
    • Same shielding, grater number of protons, stronger attraction between nucleus and outermost e-
  • with 2 exceptions
    Reasons for the exceptions
  • P subshell lower in energy than than the S subshell → less energy required to remove the e-
  • 1st e- removed from P = 1p subshell + unpaired. 1st e- removed from S = 1p subshell + paired. P= lower I.E due to e- pair repulsion. Therefore, less energy needed to remove the e- from S.
24
Q

Why does the atomic radius get smaller across the period?

A
  • same shielding
  • number of protons increases
  • greater attraction between nucleus and electrons
25
Q

What 2 factors does the mass spectrometer measure?

A

1) relative abundance
2) mass/charge (m/z) ratio

26
Q

Name the different parts of the mass spectrometer:

A
27
Q

Why is the inside of the mass spectrometer a vacuum?

A

To prevent any of the particles being tested from colliding with molecules from the air

28
Q

Name the 2 ionisation methods

A

1) electron impact
2) electrospray

29
Q

Describe the acceleration step in mass spectrometry?

A

+ve ions attracted towards the -vely charged plate and accelerate towards it. amount of acceleration depends on the m/z ratio. High m/z ratio ions will accelerate slower than low m/z ratio ions. Once accelerated, all ions will have the same KE

30
Q

Describe ion drift in mass spectrometry

A

Some ions pass through the hole in -vely charged plate, & travel along the flight tube towards detector. Travel at diff speeds = drift apart.

31
Q

Describe detection in mass spectrometry

A

ions arrive at detector at diff time due to diff velocities. ‘Time of flight’ recorded as each ion hits detector and gains an e-, which generates a current, the size of which is proportional to the abundance of each type of ion

32
Q

Describe data analysis in mass spectrometry

A

the signal from the detector is passed to a computer which generates an electric current

33
Q

Why are sample particles ionised?

A

1) so they can accelerate towards the negatively charged plate
2) so they can generate a current when they hit the detector

34
Q

How is the ion accelerated?

A

1) +ve ion attracted towards the -vely charged plate
2) all ions have the same KE

35
Q

How are ions separated in the flight tube?

A

Low m/z ions travel at higher speeds + move ahead of those travelling more slowly (high m/z)

36
Q

How are ions detected?

A
  • each ion hits the detector
  • ion gains an e-
  • generate a current
  • size of current is proportional to the abundance of the ion
37
Q

How do you find the mass from a m/z ratio?

A

M/Z value - 1 (1=charge)

38
Q

Describe electrospray ionisation as a method of ionisation:

A
  • sample is dissolved in a volatile solvent
  • sample is injected through a hypodermic needle at a high voltage, producing a fine mist
  • sample is ionised by gaining a proton
39
Q

Give an example equation for electrospray ionisation:

A

(H+ = proton)
X + H+ → XH+

40
Q

Describe electron imoact as a method of ionisation:

A
  • sample is vapourised
  • high energy e- are fired at sample
  • from an e- gun
  • 1 e- is knocke doff each particle
41
Q

Give an example equation for electron impact:

A

X (g) → X+ (g) + e-

42
Q

Ar equation

A
43
Q

KE equation

A

KE = 1/2 mv^2

44
Q

Equation to work ou the mass of 1 atom of an element:

(in kg)

A

convert the Mr to kg mol^-1 by ÷1000
then divide this by Avagadro’s constant

45
Q

Molecular Ion Peaks for e- impact

What is the peak with the largest m/z value called?
What is the peak with an m/z of 15 caused by?

A
  • peak with largest m/z ratio called the ‘Molecular Ion’ peak
  • fragment caused by +CH3 ion
46
Q

What is the m/z ratio of the molecular ion equal to?

A

the Mr of the whole molecule

47
Q

Find the relative abundances of isotopes of Br2

Exist as 79Br and 81Br isotopes. 50% abundance of each

A

1:2:1

Personal CHEM (17 decks)

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