1.1- Atomic Structure

Question 0

Details of a neutron?

Answer 0

In the nucleus

Relative mass= 1

Relative charge= 0

Question 1

Details of a proton?

Answer 1

In the nucleus

Relative mass = 1

Relative Charge = +1

Question 2

Details of electron?

Answer 2

In orbit around nucleus

Relative mass= 1/1800

Relative charge= -1

Question 3

Define atomic number?

Answer 3

Number of protons in the nucleus (Z)

Question 4

Define mass number?

Answer 4

Total number of protons and neutrons in the atom (A)

Question 5

Number of neutrons?

Answer 5

A-Z

Question 6

Define isotopes?

Answer 6

Atoms with the same number of protons but different numbers of neutrons

Same chemical properties (same electronic structure)

Varying physical properties (different masses)

Question 7

Steps in mass spectrometry?

Answer 7

Ionisation- vapourised sample injected at low pressure and an electron gun fires high energy electrons at the sample which knocks out an outer electron forming positive ions with different charges

Acceleration- negative electric field accelerates the positive ions and makes them into a beam

Deflection- The beam of positive ions is deflected by a strong magnetic field. The degree of deflection depends on mass to chard ratio, the smaller this ratio the larger the deflection. By varying the magnetic field ratio, ions of different m/z pass through centre

Detection- the ions reach the detector and generate a small current, which is fed into a computer for analysis

Question 8

Why do mass spectrometers need to be under a vacuum?

Answer 8

Otherwise air particles would ionise and register on the detector

Question 9

Formula for relative atomic mass?

Answer 9

R.A.M = sum of (isotopic mass*%abundance)/100

Question 10

How do you measure the Mr of a molecule using a mass spectrometry reading?

Answer 10

Peak with the largest m/z is equal to the Mr of the molecule

Question 11

How are electrons arranged?

Answer 11

Principle energy levels (1,2,3..)

Sub energy levels (s,p,d,f)

Orbitals (hold up to two electrons of opposite spin)

Question 12

How many electrons do each type of sub shell hold?

Answer 12

s- up to 2
p- up to 6
d- up to 10
f- up to 14

Question 13

How to atoms fill up the sub shells (up to 4p)?

Answer 13

1s 2s 2p 3s 3p 4s 3d 4p

3d is higher in energy than 4s so gets filled after 4s

Question 14

Define first ionisation energy?

Answer 14

Enthalpy change when one mole of gaseous atoms forms one mole of gaseous ions with a single positive charge

H(g) –> H+(g) + e-

Question 15

Three main factors affecting ionisation energy?

Answer 15

1. Attraction to the nucleus (nuclear charge)
2. Distance of electrons from the nucleus
3. Shielding of attraction of the nucleus

Question 16

Why is the successive ionisation energies always larger?

Answer 16

When the first election is removed the attraction from the nucleus increases as a positive ion is formed. The ion increases the attraction on the remaining electrons so the energy required to remove the next electron is larger

Question 17

Define periodicity?

Answer 17

Repeating pattern across a period

Question 18

Why has He got the largest first ionisation energy?

Answer 18

It’s first electron is in the shell closest to the nucleus and has no shielding effects from inner shells. He has a bigger first IE than H as it has one more proton

Question 19

Why do first IE decrease down a group?

Answer 19

As one goes down a group, the outer electrons are found in shells further from the nucleus and are more shielded by inner shell electrons so the attraction of the nucleus become smaller

Question 20

Why is there a general increase in first ionisation energy across a period?

Answer 20

As one goes across a period the electrons are being added to the same shell which has the same distance from the nucleus and same shielding effect. The number of protons increases, however, making the effective attraction of the nucleus greater

Question 21

Why has Na a much lower first IE than Ne?

Answer 21

Na will have its outer electron in a 3s shell further from the nucleus and is more shielded so the effective attraction from the nucleus is lower.

Question 22

Why is there a small drop from Mg to Al?

Answer 22

Al is starting to fill a 3p sub shell, whereas Mg has its outer electrons in the 3s sub shell. The electrons in the 3p sub shell are slightly easier to remove and has a lower ionisation energy

Question 23

Why is there a small drop from P to S?

Answer 23

With sulphur there are 4 electrons in the 3p sub shell and the 4th is starting to doubly fill up the first 3p orbital. When the second electron is added to an orbital there is slight repulsion between the two negatively charged electrons which makes the second electron easier to remove