8.4 ionisation énergies
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Period 3: Na, Mg, Al, Si, P, S, Cl, Ar Why does first ionisation energy drop between Mg and Al, when its supposed to be increasing across a period
Mg: 1s2 2s2 2p6 3s2 Al: 1s2 2s2 2p6 3s2 3p1 Mg loses a 3s electron whilst Al loses a 3p electron. The p electron is already at a higher energy level than the s electron so it takes less energy to remove
Period 3: Na, Mg, Al, Si, P, S, Cl, Ar Why does first ionisation energy drop between P and S
Electrons in a pair will be easier to remove than one In its own orbital because its already being repelled by the other electron P shell has 3 orbitals, so 3 pairs. P: 1s2 2s2 2p6 3s2 3p3 Has no paired electrons in a p orbital because each p electron is in its own orbital. S: 1s2 2s2 2p6 3s2 3p4 Has two of its p electrons paired in a p orbital so one of these is easier to remove than an unpaired one due to repulsion of electrons in the same orbital
What are successive ionisation energies
If you remove electrons from atoms one at a time, each one is harder to remove than the one before. E(g) —> E+(g) +e-(g) E+(g) —-> E2+(g) + +e-(g) E2+(g) —-> E2+(g) + e-(g)
How do you describe ionisation energies from a graph
. Closer to y axis, the further out the shells .Number of points before a big spike is the number of electrons on outer energy shell, so determines the group the element is in . There is a sharp increase in energy when moving down a shell because electrons are getting closer to nucleus .Energy between electrons on the same shell increase slightly