Topic 1-Atomic Structure And Periodic Table And Periodicity

Question 1

Define Relative atomic mass?

Answer 1

The weighted mean mass of an atom of an element compared to 1/12th the mass of a carbon-12 atom

Question 2

Define Relative isotopic mass

Answer 2

The mass of an atom of an isotope compared to 1/12th of the mass of a carbon 12 atom.

Question 3

What is the mass spectrometer used for?

Answer 3

The mass spectrometer is a machine which provides chemists with a way to measure and compare masses of atoms and molecules

Question 4

What are the 5 steps of mass spectrometry?

Answer 4

Vaporisation-heat up molecules so sample turns into gas so individual atoms are separated
Ionisation-An electron gun is used to knock off 1 electron via a collision causing a positive ion to be formed
Acceleration-The positive ions will move towards the negative charged detector
Deflection-A magnetic field deflects the beam of ions e.g. heavier ions will deflect less but lighter will move more
Detection-Ions will detected

Question 5

Why is a vacuum pump used in mass spectrometry,

Answer 5

To prevent ions from colliding with molecules in the air

Question 6

Define First ionisation energy?

Answer 6

The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1+ ions

Question 7

What is absorption?
What is emission?

Answer 7

When an electron moves up an electron shell
When an electron moves down an electron shell

Question 8

What is second ionisation energy?

Answer 8

Energy required to remove 1 mole of electrons from 1 mole of gaseous 1+charge to form 2+ ions

Question 9

Uses of mass spectrometers?

Answer 9

Determination of RAM of an element
Detection of drugs and their metabolites in urine
In the pharmaceutical industry

Question 10

What is an orbital?

Answer 10

Region of space outside an atoms nucleus where there there is a high probability of finding an electron with opposite spins

Question 11

What is the s block?

Answer 11

The s block comprises the elements in groups 1 and 2
The outermost electron is in an S orbital

Question 12

What is the p block?

Answer 12

Elements in group 3,4,5,6,7,8
Last electron is a p orbital

Question 13

Why is the 4s orbital below the 3d orbital

Answer 13

The 4s orbital fills below the 3d orbital because it has lower energy

Question 14

What are the three rules of an orbital

Answer 14

Aufbau principle-electrons go into the orbital with the lowest available energy
Each orbital can only contain 2 electrons with different spins
When there are 2 or more orbitals at the same energy, they fill singly before electrons pair up

Question 15

What is shielding?

Answer 15

Electron to electron repulsion,repulsion increases energy of the electrons above value they would have had

This decreases nucleur charge

Question 16

What is Effective nucleur charge?

Answer 16

Net charge on a nucleus,after allowing for the shielding effect of inner electrons

Question 17

Does effective nucleur charge stay the same down the group?

Answer 17

It does stay the same as increase in proton number(which increases attraction and charge) is outweighed by an increase in electron shielding

Question 18

Factors affecting energy of an electron?

Answer 18

Radius-greater radius means less ionisation energy as attraction is weaker
Sublevel-an electron from a full or half sublevel requires more energy
Shielding-greater shielding means more ionisation energy
Nucleur charge-amount of protons
Orbital in which they exist

Question 19

Why are positive ions smaller than its neutral atom?

Answer 19

An ion will lose its outer shell so has fewer electrons and shells
This decreases electron repulsion(shielding) so ENC increases
Increases attractiveness of electrons to nucleus

Question 20

Why are negative ions larger?

Answer 20

The atom would have gained one or more electrons so repulsion between them increases,attraction between nucleus and electrons decrease so shells move further away increasing atomic radius

Question 21

What is ionisation energy?

Answer 21

Amount of energy requires to remove an electron from an isolated atom

Question 22

Ionisation energies keep increasing for an element because..

Answer 22

After the first ionisation energy,positive ions will not want to lose another electron so attractive forces are stronger due to less shielding causing more energy required to break the bonds
More electrons being removed decreases atomic radius which increases attraction so more energy required to remove

Question 23

Why are ionisation energies of Transition Metals similar?

Answer 23

As you go down from one atom to the next,number of protons increase by 1 so ENC increases but so does the no of 3D electrons

The 3D electrons are most stable half full or fully full so this causes screening
The extra proton and screening cancel out

Question 24

General trends in ionisation energy?

Answer 24

Atomic number increases,the positive charge of nucleus increases do ENC increases

Ionisation energies increase as you go across a period

Ionisation energies decrease down a group

Question 25

Why does Ionisation energy decrease down a group?

Answer 25

Nuclear charge increases but this extra attraction is counteracted by a higher atomic radius and shielding so ionisation energy decreases

Question 26

Why is there a gradual increase in first 6 ionisations of oxygen?

Answer 26

As we remove the first 6 electrons,each of the remaining electrons are pulled closer together so atomic radius decreases so Attraction increases so ionisation energy increases

Question 27

Why is there an overall increase in ionisation energy across a period?

Answer 27

As we move across a period,each element gains a proton so nuclear charge increases meaning the attraction between positive nucleus and outer electrons increase,and as well as this atomic radius decreases

Question 28

Why is the some exemptions as to why the ionisation energy across a period does not always increase?

Answer 28

Some electrons are in the 2p subshell and not the 2s so it requires less energy to remove causing a decrease in ionisation energy

Question 29

Across a period,does atoms increase or decrease in size?

Answer 29

Atoms become smaller so atomic radius decreases and proton no. increases

Question 30

Do atoms become larger down a group?

Answer 30

Yes,so atomic radius increases and it has a lower electrostatic force of attraction

Question 31

Why is 2nd ionisation energy endothermic?

Answer 31

This is because incoming electron is already added to a negative ion
Energy is requires to overcome repulsive forces between electron and ion

Question 32

Explain the effect of low shielding in an atom?
Talk about IE,attraction

Answer 32

Lower shielding means lower electron repulsion,so positive nucleus will have a stronger attraction with outer most electron so electrons are pulled inwards,stronger attraction means more ionisation energy required

Question 33

Explain and show where the blips occur in ionisation energy across period 2?

Answer 33

Blips occur from group 2 to group 3 and group 5 to group 6
These blips occur as some elements are in the p subshell so there’s more shielding

Question 34

What is Hunds rule?

Answer 34

When there are 2 or more electrons with same spins,they fill up singly before filling pairs

Question 35

Why do Isotopes have the same chemical properties?

Answer 35

They have same electronic configuration and have same number of outer electrons which determine chemical properties and reactions

Question 36

Is Mass Spectrometry,Describe movement of ions in terms of mass and charge?

Answer 36

Ions with greater mass(m/z value)will move less and be deflected less

Ions with greater/multiple charges are deflected more

Question 37

How to calculate RAM from a mass spectra graph?

Answer 37

1.Multiply RIM(relative isotopic mass when m/z is 1+) by abundance respectively
2.Divide by Total abundance

Question 38

Explain trends in atomic radius in periods and groups?

Answer 38

Atomic radius decreases across a period as proton no. increases which causes outer electrons to be pulled in as there is a greater attraction between nucleus and outer electrons.

Shielding effect is same across period 2 as all outer electrons are partially shielded by 1 inner electron

Atomic radius increases down a group