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AS Level Chemistry > Unit 1 Section 3. Atomic Structure > Flashcards

Unit 1 Section 3. Atomic Structure Flashcards

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1
Q

What is the principle quantum number?

A

Each shell or energy level in an atom as a principal quantum number. The further average distance the shell is from the nucleus, the higher the energy and the larger quantum number.

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2
Q

What are electron shells divided into?

A

Sub shells that have slightly different energies. The sub shells have a different number of orbitals which can each hold up to 2 electrons.

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3
Q

What are the different types of sub shells?

A

s, p, d, f.

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4
Q

How many orbitals are in a s shell?

A

1

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5
Q

How many orbitals are in a p shell?

A

3

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6
Q

How many orbitals are in a d shell?

A

5

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7
Q

How many orbitals are in a f shell?

A

7

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8
Q

What is an orbital ?

A

The region around an atom where there is a high probability of finding an electron.

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9
Q

What is the shape of an s orbital?

A

It is a circle.

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10
Q

The maximum number of electrons in an s subshell

A

2

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11
Q

The maximum number of electrons in an p subshell

A

6

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12
Q

The maximum number of electrons in an d subshell

A

10

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13
Q

The maximum number of electrons in an f sub-shell

A

14

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14
Q

What is the shape of the d orbital?

A

There are 5 of them. 4 of them look like 4 balls stuck together all on the same plane. The 5th looks like a torus with 2 pear shaped areas coming out from each hole.

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15
Q

What is Hund’s rule?

A

Electrons fill up starting with the lowest energy levels. However when there are sub-shells with the the same energy level, they will fill up the levels singly first before they share with other electrons.
It happens with p orbitals.

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16
Q

What is the shape of an p orbital?

A

Dumbbell shaped. There are 3 of them and they are at right angles to each other.

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17
Q

What 2 atoms behave oddly in terms in electronic structure ?

A

Copper and chromium. They donate a 4s electron to the 3d sub shell. Because a full or half full d sub shell is more stable.

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18
Q

What is the exception to the statement that electrons always fill up from the sub shell with the smallest amount of energy up?

A

This remains true. However the 4s sub shell has less energy than the 3d sub shell so it will fill up first.

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19
Q

What is the s block of the periodic table?

A

The group 1 and 2 metals.
They will lose their one or two outer shell electrons to form negative ions with an inert gas configuration. That is to say they become un reactive because they have a full outer shell.

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20
Q

What is the d block of the periodic table?

What do they tend to do?

A

The transition metals.

Lose s and d electrons to form positive ions.

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21
Q

What is the p block of the periodic table?

A

The atoms from group 3 to group 0.

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22
Q

Define ionisation energy.

A

The energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

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23
Q

What can affect the ionisation energy?

A

The distance the electron is from the nucleus.
The more electrons, the more they will repel each other.
Reduced nuclear charge.
Electron shielding.

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24
Q

How does nuclear charge affect ionisation energy?

A

The more protons the larger the attractive force to the nucleus.
However if electrons are in different shells then the inner shell electrons decrease the pull.
In lithium the nucleus has 3 protons and so has an attractive force of 3 but the 2 inner shell electrons take some of this attraction so the outer selection only has an attraction of 1

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25
Q

What is the second ionisation energy?

A

The energy needed to remove an electron from an atom that has already had one removed.
The energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.

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26
Q

Why after successive ionsiations, does the energy needed increase?

A

Yes as
There is less electron shielding.
The electrons are closer to the nucleus.
The nucleus has a larger electron force.
There are less electrons to repel each other.

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27
Q

On a graph of successive ionisation energies what are the big jumps?

A

It is when a new shell is broken into.

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28
Q

What type of process is ionising an atom?

A

It is an endothermic one.

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29
Q

What is the general trend of first ionisation energies across a period?

A

It generally increases.

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30
Q

How can a graph of successive ionisation energies tell you which group the element is from?

A

Count how many electrons there are before the first big jump. This tells you the group number.

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31
Q

What do atoms in the same period all have?

A

The same number of energy levels.

32
Q

What is the general a trend with atomic radiuses in the periodic table?

A

It decreases.
The no. of protons increases meaning the electrons are pulled closer to the nucleus making the radius smaller.
The extra electrons are added to the outer shell so there isn’t much electron shielding as that happens mostly with inner electron shells.

33
Q

What can affect ionisation energies across a period?

A

Atomic radius. It increases as there are more electrons so the attractive force is less.
Nuclear charge. The nucleus has more protons meaning the electrons are draw to it by a stronger force.
Electron shielding. The inner shell electrons shield the outer shell ones meaning the ionisation energy is less.

34
Q

What is the general trend of ionisation energies across a period?

A

It increases.

35
Q

Why doesn’t electron shielding cause the ionisation energy to fall across a period?

A

All the extra electrons are in roughly the same energy level even if there are in different orbitals.
This means there’s generally little extra shielding or extra distance so it doesn’t affect the ionisation energy much.
Electrons aren’t added to the centre and those ones cause the most shielding.

36
Q

Why is there a small drop in ionisation energies between group 2 and group 3?

A

Beryllium (group 2) has the outer electron in the 2s subshell while boron(group 3) has them in 2p subshells.
The 2p sub shell has a slightly higher energy and is slightly further away. Also it is shielded from the 2s2 electrons.
This means it feels less attraction and is easier to ionise.
It is the same idea with the other elements.

37
Q

What causes the drop in ionisation energy between the group 5 and the group 6 elements?

A

E.g. Nitrogen(group5) has the 3 electrons of the 2p subshell in the 3 different orbitals a p shell has. In oxygen(group 6) the 2p sub-shell has 4 electrons in it. One of the orbitals contains 2 electrons and these 2 repel each other meaning it is easier to remove one.

38
Q

Why do the melting points of metals increase when you go along a period?

A

The metal metal bonds get stronger as there are more delocalised electrons and a decreasing radius. This causes a high charge density which means the ions are attracted to each other more strongly.

39
Q

Why do carbon and silicon have high melting points?

A

They have macromolecular structures meaning there are strong covalent bonds linking the atoms together.

40
Q

Explain the melting points of atoms after the metals and carbon and silicon.

A

There are the simple molecular substances (F”2” O”2”)
The melting points depends on the van der waals forces which are weak, meaning low melting points.
The more molecules in a molecule, the greater the forces so sulphur (S”8”) has a high boiling point.
The noble gases exist as individual atoms meaning the forces are even weaker.

41
Q

What is the polarising power of a cation?

A

The tendency of a cation to distort the electron field by pulling electrons towards it.

42
Q

Define periodicity.

A

Repeating chemical and physical properties and trends, found in atoms of the periodic table.

43
Q

What is the general trend with electrical conductivity?

A

It decreases across a group and increases across a period until you get to the non metals.

44
Q

Why do Na and Mg conduct electricity as well as each other, even though Mg has an extra electron?

A

It is because they are in the same quantum shell.

45
Q

Why are the non metals poor conductors of electricity?

A

They form covalent bonds meaning there are no free electrons.

46
Q

Why does the electrical conductivity of metals increase across a period?

A

There are more electrons and the electron shells overlap. There are billions of overlappings in the structure meaning they are many delocalised electrons.

47
Q

What is electro negativity ?

A

The measure of the attraction an atom has for the pair of electrons in a covalent bond.

48
Q

Explain the trend in electro negativity across a period.

A

It increases across a period. The nuclear charge is increasing and so electrons are pulled towards the nucleus by a greater amount.

49
Q

Explain the trend in electro negativity down a group.

A

It decreases. Extra electron shells cause shielding which counteracts the additional protons.

50
Q

What are the 5 stages of mass spectrometry?

A

Vaporisation, ionisation, acceleration, deflection, detection.

51
Q

Explain the vaporisation stage of mass spectrometry.

A

The chemicals are injected in the instrument and the high vacuum causes it to vaporise.

52
Q

Explain the ionisation stage of mass spectrometry.

A

High energy electrons are shot at the sample, knocking electrons off and producing positive molecular ions.

53
Q

Explain the acceleration stage of mass spectrometry.

A

An electronic field accelerates the ions to a high speed.

54
Q

Explain the deflection stage of mass spectrometry.

A

A magnetic field is used to deflect the ions. The lighter ones are deflected more. Some of the ions will crash into the sides but some will reach the detector. The strength of the electronic field can be changed so ions of different masses can get through.

55
Q

Explain the detection stage of mass spectrometry.

A

The ions are detected as a small current. The signal is sent to a computer and it is compared to a reference compound of a know mass and structure.

56
Q

What is the m/z ratio?

A

The ratio between the mass and the charge of an ion. As the charge is usually 1 it is normally just the mass of the ion.

57
Q

What is on the x axis of a mass spectrometry graph?

A

The m/z ratio.

58
Q

What is on the y axis of a mass spectrometry graph?

A

Relative abundance.

59
Q

How is the relative atomic mass of the element found through mass spectrometry ?

A

For each line, multiply the relative isotopic abundance by the relative isotopic mass. (x values X y values)
Add this together.
If the relative abundance was given as a % divide by 100
If not, divide by the total relative abundance of the peaks.

60
Q

What is the simplest case of fragmentation with mass spectrometry ?

A

The unstable molecular ions break into another positive ion and a neutral free radical.
This free radical won’t be registered as it won’t be moved by the electrical field.

61
Q

What is the base peak?

A

It is the tallest line on a mass spectrometry graph and it is usually given an arbitrary relative abundance of 100 so the other lines can be compared to it.

62
Q

What is the relative mass of an electron?

A

1/1836

63
Q

Why is mass spectrometry, done in a vacuum?

A

To stop contamination from other gases.

64
Q

How is the relative molecular mass found from the mass spectrometry ?

A

It is the largest m/z ratio.

65
Q

What does covalent mean?

A

Shared outer shell electrons.

66
Q

How do you find the relative molecular mass from mass spectrometry ?

A

Look at the line with the largest M/Z ratio. That is the one.

67
Q

Why wouldn’t a negative ion reach the detector in a mass spectrometer?

A

It wouldn’t be accelerated.

68
Q

What must you have with the equations of the ionisation energies?

A

Charges and state symbols. It is all a gas part from the electrons.
You should also have the equation that shows the atom becoming the gas.

69
Q

Describe the bonding in metals.

A

There is a lattice of positive metal ions, all arranged in a close regular arrangement with delocalised electrons around them

70
Q

How do metals conduct electricity?

A

The delocalised electrons move in a given direction. The direction of the PD.

71
Q

Why is the melting point of magnesium greater than that of sodium?

A

Mg has more delocalised electrons and a smaller atomic nucleus. This means a larger charge density and stronger metal metal bonds.

72
Q

Why is the first ionisation energy of neon greater than that of sodium?

A

In neon the outer electrons are in a 2p sub shell but in sodium there are in a 3s sub shell. There are further away and are shielded more so feel less force.

73
Q

When drawing dot and cross diagrams, what must you remember?

A

Charges go in the top right.

There aren’t any empty outer electron shells. If an atom has lost all the outer shell electrons, don’t draw the shell.

74
Q

What are the uses of mass spec?

A

Testing sport mens for steroids.

Testing samples form space.

75
Q

What is the trend with the melting points of atoms across period 3 ?

A

From sodium to aluminum it increases as the no. of electrons increases meaning a greater charge density in the metallic structure.
Silicon also has a high boiling point as it forms a giant covalent structure with many covalent bonds.
From phosphorus to argon, there are only van der waals forces of attraction between the molecules and these depend on the size of the molecule. Phosphorus has 5 atoms, sulphur has 8, chlorine 2, argon 1.

76
Q

What is the trend with the melting points of atoms across period 2 ?

A

From lithium to beryllium it increases as they form metallic bonds and the electron density increases.
In boron it forms covalent bonds as does carbon, meaning increasing boiling points. At nitrogen it falls as the molecules from here onwards are small diatomic ones held together only by van der waals.

77
Q

What is the trend with the ionization energies across period 2 of the periodic table?

A

It generally increases because of a greater charge in the nucleus. There are 2 exceptions.
Boron is lower than expected as it is the first time an electron is in the 2p sub-shell. It is shielded by the 2s shell and is further away from the nucleus meaning it is easier to remove.
oxygen is lower than expected as in there are 4 electrons in the 2p subshell. Thus there are 2 in a single subshell meaning that they repel each other meaning one is easier to remove.
It is the same idea with the atoms below them in period 3.

AS Level Chemistry (16 decks)

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