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7 Cards in this Set
- Front
- Back
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Define first ionisation energy |
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions. |
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What is the general trend of 1st ionisation energy across a period? |
General increase |
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Why is there a small decrease in 1st ionisation energy between Be and B in period 2 and Mg and Al in period 3? |
Because the electron to be removed is in a p orbital instead of a s orbital, so is slightly further away from the nuclear energy (p orbitals have higher energy) |
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Why is there a small decrease in 1st ionisation energy between N and O in period 2 and P and S in period 3? |
Because the electron to be taken is paired in a p orbital so experiences more repulsion and is easier to take. |
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Why does ionisation energy increase across a period? |
More protons in the nucleus, so a greater attraction on the electrons. |
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What is the general trend for ionisation energy down a group? |
Decreases down the group. |
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Why does 1st ionisation energy decrease down a group? |
Because there are more shells so a greater atomic radius and more electron shielding, making the outer electron easier to take. |
