atomic structure

Question 1

how are electrons arranged?

Answer 1

in a series of orbitals

Question 2

what are orbitals?

Answer 2

areas of space where electrons may be found

Question 3

what does each principle energy level (same as period) contain?

Answer 3

a number of sub-levels, which consist of a number of orbitals

Question 4

how many electrons can each orbital contain?

Answer 4

2

Question 5

what is hund’s rule?

Answer 5

electrons enter orbitals with the same energy so that each one is in a single orbital. electrons are then added to pair them, which avoids unfavourable spin-spin repulsion

Question 6

what is the order of filling?

Answer 6

s, p, d, f

Question 7

what is the electron configuration of chromium?

Answer 7

1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^5

Question 8

what is the electron configuration of copper?

Answer 8

1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^10

Question 9

define first ionisation energy

Answer 9

the energy required to move one mole of electrons from one mole of gaseous atoms to form one mole of gaseous +1 ions

Question 10

which electron is removed first in ionisation?

Answer 10

the electron from the highest energy level as this requires the least energy

Question 11

what happens to ionisation energy down a group?

Answer 11

decreases. at the atomic radius increases, the outer electrons are further from the attractive power of the nucleus. this makes them easier to remove. outer electrons are ‘shielded’ from the nuclear attraction by the electrons between them

Question 12

what happens to ionisation energy across a period?

Answer 12

nuclear charge increases across period, shielding stays the same, therefore greater attraction between nucleus and outermost electrons

Question 13

why is the ionisation energy for aluminium lower than that of magnesium?

Answer 13

in aluminium, outer electron is in the 3p sub-level, which is higher in energy than the 3s, making it easier to remove.

Question 14

why is the ionisation energy for sulfur lower than that of phosphorous?

Answer 14

P is 3p^3 whilst S is 3p^4. there is repulsion between the two paired electrons in S, making it easier to remove the electron.

Question 15

why is there a large gap between the 1st and 2nd ionisation energies for aluminium?

Answer 15

in 2nd ionisation energy, electron is now being removed from the 3s sub-level rather than the 3p. 3s is closer to the nucleus therefore greater nuclear attraction.

Question 16

why is there a large gap between 3rd and 4th ionisation energies of aluminium?

Answer 16

4th electron is removed from the second principle energy level.

Question 17

why is there an overall increase in ionisation energy?

Answer 17

nuclear charge stays the same and more easily attracts the remaining electrons

Question 18

equation for first ionisation energy of sodium:

Answer 18

Na(g) –> Na+(g) + e-

Question 19

what does the atomic number tell us?

Answer 19

the number of protons present in an atom

Question 20

what does the mass number tell us?

Answer 20

the number of protons and neutrons present in the nucleus

Question 21

what are isotopes?

Answer 21

atoms of the same element that have different numbers of neutrons

Question 22

how do the properties of isotopes differ?

Answer 22

they will have the same chemical properties as the number of electrons are identical
have different physical properties as one has atoms of a heavier mass

Question 23

what is the equation for relative atomic mass

Answer 23

∑ isotope mass x isotope abundance / ∑isotopic abundances

Question 24

what is mass spectroscopy used for?

Answer 24

used to measure the relative masses of isotopes very accurately, gives info on the relative abundance of isotopes, can also be used to identify elements

Question 25

what is electron impact ionisation?

Answer 25

the sample is injected into the inlet and vaporised. high energy electrons knock out an electron from the sample causing it to become positively charged

Question 26

what is electrospray ionisation?

Answer 26

sample dissolved in a volatile solvent. injected at a high voltage to give a fine mist. particles are ionised by gaining a proton (H+ ion) from the solvent as the leave the needle X(g) + H+ ---> XH+(g)

Question 27

what is acceleration?

Answer 27

the ions are accelerated by an electric field of fixed strength. this gives all the same amount of kinetic energy

Question 28

what is drift?

Answer 28

ions travel down a long tube. time taken to reach the detector at end depends on their mass/charge ratio. heavier, lower charged ions travel more slowly than lighter, higher charged ions. the time taken to reach the detector is called the flight time

Question 29

what is detection?

Answer 29

the ions reach the detector and gain an electron which causes an electrical pulse which can be measured. the ions are distinguished by the time they hit the detector. this is then interpreted by a computer to produce a mass spectrum.