1 atomic structure Flashcards Preview

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Flashcards in 1 atomic structure Deck (14):
1

nucleus

the tiny positively charged centre of an atom composed of protons and neutrons

2

nucleons

protons and neutrons - the sub-atomic particles found in the nuclei of atoms

3

strong nuclear force

the force that holds protons and neutrons together within the nucleus of the atom

4

electrostatic forces

the forces of attraction and repulsion between electrically charged particles

5

proton/atomic number Z

the number of protons in the nucleus of an atom

6

mass number A

the number of protons and neutrons in the nucleus of an atom

7

isotope

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

8

molecular ion

in mass spec - a molecule of the sample which has been ionised but has not broken up during its flight through the instrument

9

atomic orbital

a region of space around an atomic nucleus where there is high probability of finding an electron

10

ionisation energy IE

the energy required to remove a mole of electrons from a mole of isolated gaseous atoms/ions (kJ/mol)

11

successive ionisation energy

the energy required to remove another mole of electrons from a mole of isolated gaseous atoms/ions

12

time of flight mass spectrometry (8+6)

-accurate info on isotope Mr and abundance
-identify elements
-determine Mr
-determines the mass of separate atoms/molecules
-used to identify diff isotopes that make up element by detecting indiv ions and their masses
-high res = 5dp, low res = 1dp
-principle: form ions from sample, separate ions according to ratio of charge to mass

"electrospray ionisation"
- substance in sample converted to +ve ions, accelerated to high speeds (depending on their m/z ratio), and arrive at detector.

1. vacuum - whole apparatus kept under high vacuum to prevent ions produced colliding w molecules in air

2. ionisation - sample is dissolved in a volatile solvent, forced through a fine hollow needle that's connected to the +ve terminal of a high voltage supply. produces tiny +vely charged droplets that have lost e- to the +ve charge of the supply. solvent evaporates from droplets into the vacuum and droplets get smaller until they contain no more than a singly +ve ion

3. acceleration (to give all ions constant kinetic energy) - +ve ions attracted towards a -vely charged plate and accelerate towards it. lighter ions and highly charged ions achieve a higher speed

4. ion drift - ions pass through a hole in plate, forming a beam and travel along flight tube, to a detector

5. detection - flight times are recorded and ions pick up an electron from detector, causing a current to flow

6. data analysis - signal from detector passed to a computer which generates a mass spectrum

13

s orbital

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14

p orbital

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