3-1-1-2-mass-number-and-isotopes-chemsheet.pptx

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1. ToF MASS SPECTROMETRY www. CHEMSHEETS .co.uk © www.chemsheets.co.uk AS 1011 15-July-2016

2. © www.chemsheets.co.uk AS 1011 15-July-2016 Stage 1 – IONISATION Elements and low M r compounds X(g)  X + (g) + e – e.g. Mg(g)  Mg + (g) + e – Loss of electron

3. © www.chemsheets.co.uk AS 1011 15-July-2016 Stage 1 – IONISATION High M r compounds (e.g. proteins) X(g) + H +  XH + (g) gains a proton

4. Stage 2 – ACCELERATION © www.chemsheets.co.uk AS 1011 15-July-2016

5. Stage 3 – FLIGHT TUBE © www.chemsheets.co.uk AS 1011 15-July-2016 Lighter particles move faster and so have a shorter time of flight

6. © www.chemsheets.co.uk AS 1011 15-July-2016 Stage 3 – FLIGHT TUBE

7. © www.chemsheets.co.uk AS 1011 15-July-2016 Stage 4 – DETECTION + ve ions hit – ve plate and produce electric current size of current proportional to number of ions

8. Copper © www.chemsheets.co.uk AS 1011 15-July-2016 The Mass Spectrum

9. Average mass 2 balls with mass 100 g 3 balls with mass 200 g 10 balls with mass 400 g average mass = total mass of all balls number of balls = (2x100)+(3x200)+(10x400) 2+3+10 = 4800 = 320 g 15 © www.chemsheets.co.uk AS 1011 15-July-2016

10. 800 g loaf 400 g loaf I have these loaves – what is the average mass? average mass = total mass of all loaves number of loaves = (4x400)+(10x800) 4+10 = 9600 = 686 g 14 © www.chemsheets.co.uk AS 1011 15-July-2016

11. Neon © www.chemsheets.co.uk AS 1011 15-July-2016

12. ISOTOPES Ions with different isotopes produce different signals. Most important for Br and Cl. Br: 50% 79 Br 50% 81 Br Cl: 75% 35 Cl 25% 37 Cl If two or more Br/Cl atoms, then spectrum is more complicated. Often small peaks at m/z + 1 due to 2 H and 13 C. © www.chemsheets.co.uk AS 1011 15-July-2016

13. butane CH 3 CH 2 CH 2 CH 3 M r = 58 [ CH 3 CH 2 CH 2 CH 3 ] + [ CH 3 CH 2 CH 2 CH 3 ] + with 1 x 2 H/ 13 C © www.chemsheets.co.uk AS 1011 15-July-2016

14. butanone CH 3 CH 2 COCH 3 M r = 72 © www.chemsheets.co.uk AS 1011 15-July-2016

15. chlorine Cl 2 © www.chemsheets.co.uk AS 1011 15-July-2016

16. bromomethane CH 3 Br [CH 3 81 Br] + [CH 3 79 Br] + © www.chemsheets.co.uk AS 1011 15-July-2016

17. chloromethane CH 3 Cl [CH 3 37 Cl] + [CH 3 35 Cl] + © www.chemsheets.co.uk AS 1011 15-July-2016