Physical Chemistry- Atomic Structure Flashcards

1
Q

What is the charge and mass of:
Proton
Neutron
Electron

A

Charge
P- +1
N- 0
E- -1

Mass
P-1
N-1
E-1/1840

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2
Q

What decides the chemical properties of an element?

A

Electron configuration

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3
Q

Why do isotopes have the same chemical properties?

A

They have the same electron configuration

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4
Q

Why do isotopes have slightly different physical properties?

A

Physical properties depend on the mass of the atom. Isotopes have different mass numbers.

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5
Q

What is the relative atomic mass?

A

The average mass of an atom of an element relative to 1/12th the mass of one atom of carbon-12

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6
Q

What is relative isotopic mass?

A

Mass of an isotope relative to 1/12th the mass of one atom of carbon-12

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7
Q

How to calculate relative atomic mass?

A

(Isotopic mass x percentage abundance)/100

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8
Q

What does a mass spectrometer calculate?

A

Relative atomic mass of an element and relative abundance of its isotopes

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9
Q

What are the four stages of mass spectrometry?

A

1) Ionisation
2) Acceleration
3) Ion drift
4) Detection

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10
Q

What is electron impact ionisation?

A

1) Sample is vapourised
2) Electron gun fires a high energy electron at sample causing for an electron to be knocked off
3) A +1 ion is formed

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11
Q

What is electro spray ionisation?

A

1) Sample is dissolved in a volatile solvent
2) Sample is injected into mass spectrometer through a hypodermic needle to give a fine mist
3) Tip of the needle is attached to the positive terminal of a high voltage supply
4) A high voltage is applied causing for it to gain a proton
5) The solvent is removed, leaving a gas
NB- sample increases in mass by 1 (+H)

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12
Q

What happens during acceleration?

A

An electric field accelerates the positive ions.
It gives the same kinetic energy to the ions with the same charge.
Lighter ions experience a greater acceleration than heavier ions

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13
Q

What happens during ion drift?

A

Ions enter a region with no electric field
They drift through the region at same speed as they left the electric field

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14
Q

What happens during detection?

A

The positive ions hit the detector
They gain an electron= causes for current to be produced
Detector detects current produced and time taken for ion to pass through spectrometer= size of current is directly proportional to abundance of the ion

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15
Q

Why must the sample be ionised?

A

So that it can be detected and accelerated = electric field will only accelerate ions

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16
Q

Why must the spectrometer be kept under vacuum?

A

Prevents the ions colliding with air moleules

17
Q

What are the different types of sub-shells?

A

s sub-shell = 1 orbital = 2 electrons
p sub-shell = 3 orbitals = 6 electrons
d sub-shell = 5 orbitals = 10 electrons
f sub-shell = 7 orbitals = 14 electrons

18
Q

What is an orbital?

A

An orbital holds up to 2 electrons that have opposite spins

19
Q

Define molecule

A

Two or more atoms covalently bonded together (Cl2, H2, H2O, CO2)

20
Q

Define compound

A

Two or more different types of atoms ionically/covalently bonded together

21
Q

Formulae of acids
Hydrochloric acid
Nitric acid
Sulfuric acid
Phosphoric acid

A

HCl
HNO3
H2SO4
H3PO4

22
Q

Define an acid

A

A substance that donates H+ ions/protons

23
Q

Define a base

A

A substance that accepts H+ ions/protons

24
Q

Define an alkali

A

A base that releases OH- ions in an aqueous solution

25
Q

Define ionisation energy

A

Ionisation energy is the amount of energy required to remove one mole of electrons from one mole of atom in the gaseous state

26
Q

What factors affect ionisation energy?

A

1) Distance between e- to be removed and nucleus
2) Amount of shielding
3) Number of protons

27
Q

Explain the trend of the first ionisation energy down a group

A

IE decreases
More shielding
More shells
Greater atomic radius
So force of attraction between nucleus and outer electron is weaker = less energy is required

28
Q

Explain the trend of the first ionisation energy across a period

A

IE increases
Same shielding and number of shells
Number of protons in nucleus increase = more attraction between nucleus and outer electron = more energy is required

29
Q

Example of a deviation in trend of IE across a period

A

Group 2: Be - B
Group 3: Mg - Al
E- being removed in B is in the 2p subshell = further away from nucleus = more shielding = weaker force of attraction between nucleus and outer e-

30
Q

Why do successive IEs increase?

A

Each subsequent electron needs greater IE to be removed from a more positive ion = attraction between the nucleus and outer electron is stronger