Flashcards
Ionisation Energy
Cards in this deck (14)
- 1First ionisation energyThe first ionisation energy of an element is the energy required to remove one electron from each atom of one mole of gaseous atoms to form one mole of gaseous 1+ ions.
- 2What affects ionisation energy?•Electrons are held in their shells by their attraction to the positive nucleus.
•This attraction must be overcome to remove an electron.
•The outer electrons are furthest away as so they are least attracted.
•Therefore they are easiest to remove and are removed first. - 3The nuclear attraction is affected by three things•Atomic radius
–Greater radius = less attraction.
•Nuclear charge
–Larger charge = larger attraction.
•Electron shielding
–Inner shells repeal electrons outside them, this is called shielding or screening.
–More inner shells = lower attraction - 4Electron shielding• Electron shielding is the repulsion between electrons in different inner shells.
•Shielding reduces the net attractive force from the positive nucleus on the outer shell electrons. - 5Successive ionisation energyThe successive ionisation energies are a measure of the energy required to remove each electron in turn.
- 6Trends in successive ionisation energy•Each successive ionisation energy is greater.
•As each electron is removed there is less repulsion between the remaining electrons so they are drawn closer to the nucleus.
•As the distance decreases to the nucleus the electrons are held more strongly so more energy is required to remove them. - 7Why does ionisation energy decrease down a group ?the electron is
further from the nucleus, and has more shielding, even for the increase in nuclear charge. - 8Why does ionisation energy increase across a period ?increase in nuclear charge for the same distance from the nucleus.
- 9What factors affect ionisation energy ?1.The attraction of the nucleus
(The more protons in the nucleus the greater the attraction)
2. The distance of the electrons from the nucleus
(The bigger the atom the further the outer electrons are from the nucleus and the weaker the attraction to the nucleus)
3. Shielding of the attraction of the nucleus
(An electron in an outer shell is repelled by electrons in complete inner shells, weakening the attraction of the nucleus) - 10Why are successive ionisation energies always larger?The second ionisation energy of an element is always bigger than the first ionisation energy. When the first electron is removed a positive ion is formed.
The ion increases the attraction on the remaining electrons and so the energy required to remove the next electron is larger. - 11periodicityA repeating pattern across a period
- 12Why has Helium the largest first ionisation energy ?first electron is in the first shell closest to the nucleus and has no shielding effects from inner shells. He has a bigger first ionisation energy than H as it has one more proton
- 13Why has Na a much lower first ionisation energy than Neon?Na will have its outer electron in a 3s shell further from the nucleus and is more shielded. So Na’s outer electron is easier to remove and has a lower ionisation energy.
- 14Why is there a small drop from Mg to Al?Al is starting to fill a 3p sub shell, whereas Mg has its outer electrons in the 3s sub shell. The electrons in the 3p subshell are slightly easier to remove because the 3p electrons are higher in energy and are also slightly shielded by the 3s electrons
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- AS - Level Chemistry (Topic 1) Flashcards on Ionisation Energy, created by Emily Bowden on 24/11/2015.
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- Emily Bowden
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