Atomic structure

Question 1

Proton relative mass and charge

Answer 1

relative mass= 1

charge= +1

Question 2

Neutron relative mass and charge

Answer 2

relative mass= 1

charge= 0

Question 3

Electron relative mass and charge

Answer 3

relative mass= 1/1840

charge= -1

Question 4

What is an isotope?

Answer 4

Isotopes are atoms of the same element with the same number of protons, but different numbers of neutrons.

Question 5

Chemical properties of isotopes

Answer 5

Isotopes have similar chemical properties because they have the same electronic configuration

Question 6

Physical properties of isotopes

Answer 6

slightly varying physical properties (Density,boiling point and melting point) because they have different masses.

Question 7

How has atomic structure changed overtime?

Answer 7

GREEKS - earth, fire, water, air
J. DALTON - all matter from atoms (nothing smaller) spheres
J.J. THOMSON - plum pudding model (ball off positive charge with e- dotted around
Ernest Rutherford- gold foil experiment. Fired + charged alpha particles at a thin sheet of gold. Most passed straight through and small number deflected backwards due to positive nucleus.
BOHR - positive nucleus and e- surrounded it on shells.
CHADWICK - discovered neutron

Question 8

Element definition

Answer 8

Made up of ONLY one type of atom

Question 9

What is a TOF mass spectrometer used for?

Answer 9

Mass spectrometry can be used to identify elements.
Mass spectrometry can be used to determine relative
molecular mass.

Question 10

What information can a mass spectrometer give?

Answer 10

The mass spectrometer gives accurate information
about relative isotopic mass and also about the relative
abundance of isotopes.

Question 11

Steps of mass spectrometry

Answer 11

1. Ionisation
2. Acceleration (to give all ions same kinetic energy)
3. ion drift
4. ion detection
5. Data analysis

Question 12

Types of ionisation

Answer 12

electrospray ionisation

electron impact

Question 13

Process of TOF mass spectrometry

Answer 13

Sample is vaporised into a gas form
Ionisation: ionised by electrospray or electron impact
Acceleration: accelerated by an electric field. (charged acceleration plate attracts + ions on the back)
Now all will have same kinetic energy
Light- move faster than heavier
Ion drift: no electric field so just pass through
Lighter drift faster
Heavier drift slower
Detection: lighter detected first (shorter drift time) mass spectrum is generated using the charged ions (using electron field) form a mass spectrum graph (able to separate ions due to mass)

Question 14

Describe electrospray ionisation

Answer 14

• The sample is dissolved in a volatile, polar solvent
• injected through a fine needle giving a fine mist
• the tip of needle has high voltage
• at the tip of the needle the sample molecule, M, gains a proton
• The solvent evaporates away while the positive
ions move towards a negative plate

Question 15

Describe electron impact ionisation

Answer 15

• An electron gun is used to fire high energy electrons at the particles
• Knocks off elecrons forming + ions

Question 16

Why is TOFMS kept under vaccum?

Answer 16

to prevent interference of foreign particles from air

Question 17

What data is plotted from a TOF:MS

Answer 17

M/Z ratio (mass to charge)

Question 18

Overall Isotope Present (Ar)

Answer 18

(m/z1 x abundance1) + (m/z2 x abundance2) ….

/ total abundance

Question 19

Finding relative abundance

Answer 19

Total mass of each isotope/ 100%

Question 20

Equation for mass spectrometry

Answer 20

t=d x {sqaure root m/2KE}