topic 1

Question 1

relative mass and charge of protons, neutrons & electrosn

Answer 1

proton : 1, +1
neutron : 1, 0
electron : 0.005, -1

Question 2

atomic number

Answer 2

number of protons in an atom

Question 3

mass number

Answer 3

total number of protons and neutrons in an atom

Question 4

isotopes

Answer 4

atoms with the same number of protons but different number of neutrons

Question 5

relative isotopic mass

Answer 5

mass of one atom of an isotope compared to one twelfth of the mass of one atom of carbon-12

Question 6

relative atomic mass

Answer 6

the avg mass of an atom compared to 1/12th of the mass of a carbon-12 atom

Question 7

relative molecular mass

Answer 7

the average mass of a molecule compared to one twelfth of the mass of one atom of carbon-12

Question 8

relative atomic mass calculation from mass spectrometry

Answer 8

R.A.M =
(isotopic mass x % abundance) / 100

if relative abundance is used then:
R.A.M = (isotopic mass x relative abundance) / total relative abundance

Question 9

predicting mass spectra for diatomic molecules including Cl

Answer 9

mass spectrometry of diatomic molecules produces molecules, not individual atoms.

fragmentation occurs. This is when Cl is put through the ionisation chamber, an electron is knocked off. This produces a molecular ion, Cl2+. This ion is unstable so eventually fall apart and give a chlorine atom and a Cl+ ion.

Question 10

how can mass spectrometry be used to determine the relative molecular mass of a molecule

Answer 10

the heaviest ion - the one with the greatest m/z value - is likely to be the molecular ion.

Finding the relative molecular mass from a mass spectrum you look for the peak with the highest value for m/z, and that value is the relative formula mass of the compound

e.g. if highest m/z value is 72 then the relative molecular mass of that compound will be 72

Question 11

first ionisation energy

Answer 11

the energy required for one mole of gaseous atoms to form one mole of gaseous ions with a single positive charge

Question 12

successive ionisation energies

Answer 12

the energy that is required to remove the electron one after the other

Question 13

factors that affect ionisation energies

Answer 13

1. attraction of the nucleus (more protons in the nucleus the greater the attraction - large IE)
2. distance of the electrons from the nucleus (weaker attraction for bigger atoms - small IE)
3. shielding of the attraction of the nucleus (bigger the atom, more shielding, outer electrons repelled by inner shells - lower IE)

Question 14

why is there a general increase in first IE across a period?

Answer 14

because the proton number increases which makes the attraction to the nucleus greater. Electrons are being added to the same shell which therefore has the same shielding effect and electrons are pulled in closer to the nucleus

Question 15

why do first ionisation energies decrease down a group?

Answer 15

as you go down the group, the outer electrons are further away from the nucleus so the attraction from the nucleus decreases

Question 16

why are successive ionisation energies always larger

Answer 16

second IE is always larger than the first. this is because when the first electron is removed, a positive ion is formed. this increases attraction on the remaining electrons, so the energy required to remove the next electron is larger

Question 17

why does helium have the largest first ionisation energy

Answer 17

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

Question 18

why does Na have a much lower first ionisation energy then Neon?

Answer 18

Na will have electrons in a 3s sub-shell further from the nucleus and is more shielded. So, Na’s outer electron is easier to remove and has a lower IE

Question 19

Why is there a small drop from Mg to Al?

Answer 19

Al starts to fill 3p sub shell whereas Mg has its outer electrons in the 3s sub shell. The 3p electrons are slightly easier to remove because they are higher in energy and also less shielded than 3s electrons

Question 20

Why is there a small drop form P to S?

Answer 20

Sulphur has 4 electrons in the 3p sub-shell and the 4th is starting to doubly fill the first 3p orbital. When a second electron is added to 3p orbital, there is slight repulsion between the two electrons, hence making it easier to remove the second electron

Question 21

how did ideas about electronic configuration develop

Answer 21

1. atomic emission spectra provide evidence for the existence of quantum shells
2. successive ionisation energies provide evidence for the existence of quantum shells and the group to which the element belongs
3. first ionisation energy of successive elements provides evidence for electron sub-shells

Question 22

orbital

Answer 22

a region within an atom that can hold up to two electrons with opposite spins

Question 23

s, p, d & f blocks

Answer 23

s - 2 electrons/ orbital
p - 6 electrons/ orbital
d - 10 electrons/ orbital
f - 14 electrons/ orbital

Question 24

periodicity

Answer 24

a repeating pattern across a period