Atomic structure

Question 1

Charge of electron

Answer 1

-1

Question 2

Charge of proton

Answer 2

+1

Question 3

Charge of neutron

Answer 3

0

Question 4

Relative mass of proton

Answer 4

1

Question 5

Relative mass of neutron

Answer 5

1

Question 6

Relative mass of e-

Answer 6

1/1850

Question 7

What is mass number?

Answer 7

Total number of protons and neutrons in the nucleus

Question 8

What is atomic number?

Answer 8

The number of protons in the nucleus - it identifies the element. All atoms of the same element have the same number of protons

Question 9

How do you work out number of neutrons

Answer 9

Mass number - atomic number

Question 10

What is an isotope?

Answer 10

Atoms with the same number of protons different number of neutrons. Different mass numbers mean different numbers of neutrons

Question 11

What decides the chemical properties of an element?

Answer 11

The number and arrangement of electrons.

Question 12

Why do isotopes have the same chemical properties?

Answer 12

They have the same configuration of electrons

Question 13

What do physical properties depend on?

Answer 13

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

Question 14

John Dalton

Answer 14

Atoms were solid spheres, and said that different spheres made up the different elements

Question 15

J.J. Thomson

Answer 15

He discovered the electron. This showed that atoms weren’t solid and indivisible. The ‘solid sphere’ idea of the atomic structure had to be change - plum pudding model

Question 16

Ernest Rutherford

Answer 16

Fired +vely charged alpha particles at a very thin sheet of gold. The plum pudding model suggested that most alpha particles would be slightly deflected by the positive pudding that made up most of the atom. But, most of the particles passed straight through the gold with small numbers being deflected backwards. This meant plum pudding model was wrong. Rutherford developed nuclear model. Tiny positively charged nucleus surrounded by a cloud of negative electrons - most of the atom is empty space

Question 17

Niels Bohr

Answer 17

Cloud around nucleus in Rutherford’s model would spiral down into the nucleus and atoms would collapse. Bohr new model of atom where electrons exist in shells or orbitals of fixed energy. When electrons move between shells, electromagnetic radiation (with fixed energy or frequency) is emitted or absorbed. The Bohr model fitted experimental observations of the radiation emitted and absorbed by atoms

Question 18

Current model of atom

Answer 18

Not all electrons in a shell have the same energy. This meant Bohr model isn’t fully right. They refined it to include sub-shells.

Question 19

What is Ar?

Answer 19

Relative atomic mass 0 the average mass of an atoms of an element on a scale where an atom of carbon-12 is 12

Question 20

What is Mr?

Answer 20

Relative molecular mass - the average mass of a molecule on a scale where an atom of carbon-12 is 12

Question 21

What is relative isotopic mass?

Answer 21

The mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is 12

Question 22

What are the stages of mass spec?

Answer 22

Ionisation
Acceleration
Ion drift
Detection

Question 23

What are the two methods of ionisation?

Answer 23

Electrospray ionisation
Electron impact ionisation

Question 24

Describe the first stage of mass spec

Answer 24

Electrospray - Sample dissolved and pushed through small nozzle at high pressure. High voltage is applied, causing each particle to gain an H+ ion. The sample is turned into s gas made up of positive ions
Electron impact - Sample vapourised and electron gun is used to fire high energy electrons at it. This knocks one electron off each particle, so they become +1 ions

Question 25

Describe second stage of mass spec

Answer 25

Acceleration - positively charged ions are accelerated by an electric field so that they all have the same kinetic energy. (lighter ions will end up moving faster than heavier ones)

Question 26

Describe the third stage of mass spec

Answer 26

Ion drift - Ions enter a region with no electric field, so they just drift through it. Lighter ions will drift through faster than heavier ions

Question 27

Describe the fourth stage of mass spec

Answer 27

Detection - because lighter ions travel at higher speeds in the drift region, they reach the detector in less time than heavier ions. The detector detects charge particles and a mass spectrum is produced

Question 28

What goes on the x-axis of a mass spectrum

Answer 28

M/Z = mass/charge ratio

Question 29

What goes on the y-axis on a mass spectrum

Answer 29

Abundance of ions - often as a %

Question 30

How to find out relative atomic mass from a mass spectrum

Answer 30

For each peak, read the % relative isotopic abundance from the y-axis and relative isotopic mass from the x-axis. Multiply together to get the total mass for each isotope. Add up these totals and divide by 100 (if % used) or by sum of relative abundances

Question 31

How do you identify elements from mass spec?

Answer 31

Elements with different isotopes produce more than one line in a mass spectrum because the isotopes have different masses. This produces characteristic patterns which can be used as 'fingerprints' to identify certain elements. Many elements only have one stable isotope. They can still be identified by mass spectrum by looking for a line at their relative atomic mass

Question 32

How can you use mass spec to identify molecules?

Answer 32

A molecular ion, M+, is formed in the mass spectrometer when one electron is removed from the molecule. This gives a peak in the spectrum with a mass/charge ratio equal to the relative molecular mass of the molecule. This can be used to help identify an unknown compound

Question 34

How do electrons move around the nucleus?

Answer 34

In shells or energy levels

Question 35

What is the principal quantum number and how is it affected?

Answer 35

A number that describes the energy level of an electron in an atom. The further a shell is from the nucleus, the higher its energy and the larger its principal quantum number

Question 36

How many orbitals and electrons can sub-shells hold?

Answer 36

Have different numbers of orbitals which can each hold up to 2 electrons

Question 37

How do the electrons spin in orbitals?

Answer 37

Opposite direction

Question 38

Rules for finding out electron configurations?

Answer 38

1. Electrons fill up lowest energy sub-shells first 2. Electrons fill orbitals singly before they start sharing 3. For the configuration of ions from the s and p blocks on the periodic table, just remove or add the electrons to or from the highest energy occupied sub-shell

Question 39

What fills up first: 3d or 4s?

Answer 39

4s (except Cr and Cu)

Question 40

What are the cell notations for Cr and Cu and why?

Answer 40

They donate one of their 4s electrons to the 3d sub-shell as they're happier with a more stable full or half-full d sub-shell Cr- 1s2,2s2,2p6,3s2,3p6,3d5,4s1 Cu- 1s2,2s2,2p6,3s2,3p6,3d10,4s1

Question 41

What happens in the cell notation of transition metals when they become ions?

Answer 41

They lose their 4s electrons before their 3d electrons

Question 42

How does electronic structure decide the chemical properties of an element?

Answer 42

The number of outer shell electrons decides the chemical properties of an element

Question 43

How are s block elements decided on chemical properties due to their electronic structure?

Answer 43

Have 1 or 2 outer shell electrons. They are easily lost to form positive ions with an inert gas configuration

Question 44

How are p block elements decided on chemical properties due to their electronic structure?

Answer 44

Groups 5, 6 and 7. Can gain 1,2 or 3 electrons to form negative ions with an inert gas configuration Groups 4 to 7 can also share electrons when they form covalent bonds

Question 45

How are group 0 elements decided on chemical properties due to their electronic structure?

Answer 45

Group 0 (the inert gases) have completely filled s and p sub-shells and don't need to bother gaining, losing or sharing electrons - their full sub-shells make them inert

Question 46

How are d block elements decided on chemical properties due to their electronic structure?

Answer 46

(transition metals) tend to lose s and d electrons to form positive ions

Question 47

What is first ionisation energy?

Answer 47

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

Question 48

Is the first ionisation energy endothermic or exothermic?

Answer 48

Endothermic process as you're putting energy in to ionise an atom or molecule

Question 49

What is the equation for first ionisation energy of oxygen?

Answer 49

O(g) --> O+(g) + e- +1314KJmol-1

Question 50

Rules for ionisation energies

Answer 50

1) Must use the gas symbol, (g), because ionisation energies are measured for gaseous atoms) 2) Always refer to 1 mole of atoms, as stated in the definition, rather than to a single atom 3) The lower the ionisation energy, the easier it is to form an ion

Question 51

What are the factors affection ionisation energy?

Answer 51

Nuclear charge Distance from nucleus Shielding

Question 52

What is nuclear charge?

Answer 52

The more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction for the electrons

Question 53

What is distance from the nucleus?

Answer 53

Attraction falls off very rapidly with distance. An electron close to the nucleus will be much more strongly attracted than one further away.

Question 54

What is shielding?

Answer 54

As the number of electrons between the outer electrons and the nucleus increases, the outer electrons feel less attraction towards the nuclear charge. The lessening of the pull of the nucleus by inner shells of electrons is called shielding (or screening)

Question 55

What does a high ionisation energy mean?

Answer 55

There is a high attraction between the electron and the nucleus and so more energy is needed to remove the electron

Question 56

What is a successive ionisation energy

Answer 56

You can remove all the electrons from an atom, leaving only the nucleus. Each time you remove an electron, there's a successive ionisation energy

Question 57

What is the definition for second ionisation energy?

Answer 57

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

Question 58

What is the equation for second ionisation energy of oxygen?

Answer 58

O+(g) --> O2+(g) + e- +3388 KJmol-1

Question 59

How do successive ionisation energies show cell structure?

Answer 59

Within each shell, successive ionisation energies increase. This is because electrons are being removed from an increasingly positive ion - there's less repulsion amongst the remaining electrons, so they're held more strongly by the nucleus The big jumps in ionisation energy happen when a new shell is broken into - an electron is being removed from a shell closer to the nucleus

Question 60

Trends in first ionisation energies?

Answer 60

1) The first ionisation energies of elements go down a group of the periodic table decreases 2) The first ionisation energies of elements across a period generally increase

Question 61

Why does ionisation energy decrease down group 2?

Answer 61

If each element down group 2 has an extra electron shell compared to the one above, the extra inner shells will shield the outer electrons from the attraction of the nucleus Also, the extra shell means the outer electrons are further away from the nucleus, so that the nucleus's attraction will be greatly reduced.

Question 62

Why does ionisation energy increase across a period?

Answer 62

As you move across a period, the general trend is for the ionisation energies to increase This can be explained because the number of protons is increasing, which means a stronger nuclear attraction All the extra electrons are at roughly the same energy level, even if the outer electrons are in different orbital types This means there's generally little extra shielding effect or extra distance to lessen the attraction from the nucleus. But, there are small drops between groups 2 and 3, 5 and 6.

Question 63

How does the drop between groups 2 and 3 show sub-shell structure?

Answer 63

Aluminium's outer electron is in a 3p orbital rather than a 3s. The 3p orbital has a slightly higher energy than the 3s orbital, so the electron is, on average, to be found further from the nucleus The 3p orbital has additional shielding provided by the 3s2 electrons Both these factors together are strong enough to override the effect of the increased nuclear charge, resulting in the ionisation energy dropping slightly. This pattern in ionisation energies provides evidence for the theory of electron sub-shells

Question 64

What are drops in 5 and 6 due to?

Answer 64

Electron repulsion. This shielding is identical in the phosphorus and sulfur atoms, and the electron is being removed from and identical orbital. In phosphorus's case, the electron is being removed from a singly-occupied orbital containing two electrons The repulsion between two electrons in an orbital means that electrons are easier to remove from shared orbitals.