atomic structure notes

Question 1

what evidence was found to support Rutherford’s model?

Answer 1

majority of the helium nuclei passed through

most of the atom must be empty space

very small number of ions were deflected and reflected because nucleus is positive and dense

Question 2

ionisation energy

Answer 2

the energy required to removed one mole of electrons from one mole or gaseous atoms

Question 3

Three key factors that Will influence lonisation Energy

Answer 3

Nuclear Charge (the number of protons in the nucleus)

Distance from the nucleus

Shielding

Question 4

The following data shows the first seven successive ionisation energies of a period 3 element. State which element it is and explain your reasoning.

Answer 4

• The biggest jump is between the 4th and 5th ionisation energies
• the 5th electron is on the shell closer to the nucleus
• The element must have 4 electrons on its outer shell
• in period 3 this must be Silicon.

Question 5

Why is Li a bigger atom than Be?

Answer 5

same shielding

Be has more protons

so attracts outer electron more strongly

Question 6

Why is Li a bigger atom than He?

Answer 6

Li has more protons

Li has more shielding

Li has a bigger atomic radius

the outer electron is less strongly attracted to the nucleus

Question 7

Why is Li a bigger atom than F?

Answer 7

same shielding

F has more protons

more strongly attracts outermost electron

Question 8

Why is Li+ a smaller ion than F-?

Answer 8

F- has more shielding

the outermost electron is less strongly attracted to nucleus

Question 9

The 1stIE will increase

Answer 9

more protons

shielding stays the same

Question 10

Within the s sub-shell there is…

Answer 10

one S orbital

Question 11

Within the p sub-shell there are…

Answer 11

3 P orbitals

Question 12

Within the d sub-shell there are

Answer 12

5 D orbitals

Question 13

Exceptions for electron configurations of d-block atoms and ions:

Exception 1 - Chromium

Answer 13

1S2 2S2 2p6 3s2 3p6 4s1 3d5

Question 14

Exception 2 - Copper

Answer 14

1s2 2s2 2p6 3s2 3p6 4s1 3d10

Question 15

How does the ionisation energy change down a group?

Answer 15

atom gets bigger

more shielding

weaker attraction between outermost electron and nucleus

ie decreases down group

Question 16

Q: Why does the atomic radius gets smaller from right to left across a period?

Answer 16

number of protons increases

greater attraction between outermost electron and nucleus

shielding stays same

Question 17

the mass spectrometer measure two factors:

Answer 17

relative abundance

mass to charge ratio

Question 18

why is mass spectrometry in a vacuum?

Answer 18

to prevent any of the particles being
tested colliding with molecules from the air.

Question 19

a: Why are the sample particles ionised?

Answer 19

So they can be accelerated towards the negatively charged plate
So they generate a current when they hit the detector

Question 20

How is the ion accelerated?

Answer 20

Positive ions attracted to the negatively charged plate
All ions have the same kinetic energy

Question 21

How are ions separated in the flight tube?

Answer 21

lons travelling at higher speeds (small m/z) move ahead of those travelling more
slowly (large m/z)

Question 22

How are the ions detected?

Answer 22

Each ions hits the detector
Ion gains an electron
Generates a current
Size of the current is proportional to the abundance of the ion

Question 23

Electron impact

Answer 23

sample being analysed is vaporised and then high energy electrons are fired at it
the high energy electrons come from an “electron gun’ which is a hot wire filament with a
current running through it that emits electrons.
This usually knocks off one electron from each particle forming a 1*ion.

Question 24

Calculating Ar
This is often used to calculate the relative atomic mass (A) of elements.
Key Formulae:

Answer 24

Ar= (Mass 1 x Abundance 1) + (Mass 2 x Abundance 2) + (Mass n x Abundance)
————————————
sun of Abundances

Question 25

KE=

Answer 25

KE = ½ mv2

Question 26

KE rearranged for M

Answer 26

m = KE
——-
1/2V2

Question 27

KE reg arranged for V2

Answer 27

V2= KE
————-
1/2M