Atomic Structure

Question 1

What is the relative mass and charge of particles in an atom?

Answer 1

Proton = (mass) 1, (charge) +1
Neutron = (mass) 1, (charge) 0
Electron = (mass) 1/1840, (charge) -1

Question 2

What is the exact mass and charge of particles in an atom?

Answer 2

Proton = (mass) 1.673×10^-27, (charge) +1.602×10^-19
Neutron = (mass) 1.675×10^-27, (charge) 0
Electron = (mass) 0.911×10^-30, (charge) -1.602×10^-19

Question 3

Define Isotope.

Answer 3

Atoms that have the same atomic number, different atomic mass so same number of protons, different number of neutrons.

Question 4

Why do isotopes behave the same chemically?

Answer 4

They have the same number of electrons which determines the chemical behaviour of elements.

Question 5

What is Mass Spectroscopy?

Answer 5

Analytical technique that identifies different isotopes and finds the relative atomic mass of the element.

Question 6

Where can Mass Spectroscopy be used?

Answer 6

Used by forensic scientists (identify substances), and space probes (identify carbon compounds in rock samples).

Question 7

What are the 5 stages of Time of Flight Mass Spectroscopy?

Answer 7

1. Vaporisation
2. Ionisation
3. Acceleration
4. Deflection/ Ion Drift
5. Detection

Question 8

What is Vaporisation in TOF?

Answer 8

Substance is vaporised (gas) and injected into vacuum (to prevent colliding with air).

Question 9

Describe Electrospray Ionisation

Answer 9

Tiny droplets of the molecule become positively charged. Vacuum causes solvent to evaporate, leaving MH+ to be attracted to negative plate.

Question 10

Give the equation for Electrospray Ionisation.

Answer 10

M (l) + H+ -> MH+ (g)

M= Molecule
H+ = proton from solvent

Question 11

Why is Electrospray Ionisation used for?

Answer 11

Used to detect high Mr Molecules.

Question 12

What is Electron Impact Ionisation?

Answer 12

Electron gun (high voltage) fires causing high-energy electrons to take/knock an electron from the sample, forming positive ions.

Question 13

What is the equation for electron impact ionisation?

Answer 13

X (g) -> X+ (g) + e-

Question 14

What is electron impact ionisation used for?

Answer 14

Used for elements and low Mr Compounds.

Question 15

Describe Acceleration in TOF

Answer 15

Positively charged ions are attracted to the negatively charged plate and accelerated to the same kinetic energy.

Question 16

Describe Ion Drift in TOF

Answer 16

Ions pass through a hole in the plate and form a beam to travel along the flight tube towards the detector.

Question 17

What is Detection in TOF?

Answer 17

Positive ions pick up an electron from the detector, vausing current to flow. Size of current is proportional to relative abundance.

Question 18

What are orbitals?

Answer 18

Clouds of negative charge which electrons are in.

Question 19

How many orbitals are in each sub-level?

Answer 19

S = 1 (2e-)
P = 3 (6e-)
D = 5 (10e-)
F = 7 (14e-)

Question 20

Identify the sub-level blocks on the Periodic Table.

Answer 20

S-Block = G1, G2, He
P-Block = G3, G4, G5, G6, G7, G0
D-Block = Transition Metals
F-Block = Radioactive Elements

Question 21

What are element exceptions in electron configuration?

Answer 21

Cr = 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Cu = 1s2 2s2 2p6 3s2 3p6 4s1 3d10

Question 22

What is the electron configuration of the two exceptions as ions?

Answer 22

Cr3+ = 1s2 2s2 2p6 3s2 3p6 3d3
Cu2+ = 1s2 2s2 2p6 3s2 3p6 3s9

Question 23

Define Ionisation Energy.

Answer 23

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

Question 24

Give the general equation for Ionisation Energy.

Answer 24

X (g) -> X+ (g) + e-

Question 25

What is the trend in ionisation energy down the group?

Answer 25

Decreases.
Increasing atomic radius means more shielding which means weaker forces of attraction between nucleus and outer shell electron.

Question 26

How do successive ionisation energy diagrams give evidence for the atomic orbital theory?

Answer 26

Sudden increases in energy level indicate the big jump in energy needed to remove an outer electron from a sub-level closer to the nucleus.