Atomic Structure: Electron Configuration - Ionisation Energies Flashcards

1
Q

First Ionisation Energy

A
  • The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of +1 ions
  • X(g) → X+(g) + e‒
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2
Q

Second Ionisation Energy

A
  • The second ionisation energy involves the removal of a second electron
  • X+(g) → X2+(g) + e‒
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3
Q

Factors Affecting Ionisation Energies

A
  • A high ionisation energy means there’s a high attraction between the electron and the nucleus, so more energy is needed to remove the electron

• Nuclear charge
- The more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction for the electrons

• Distance from the nucleus

  • Attraction falls off very rapidly with distance
  • An electron close to the nucleus will be much more strongly attracted than one further away

• Shielding

  • As the number of electrons between the outer electrons and the nucleus increases, the outer electrons feel less attraction to the nucleus
  • This lessening of the pull thanks to the inner electrons is called shielding
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4
Q

Explain drastic increases in ionisation energies

A
  • Large jumps in the ionisation energy reveal where electrons are being removed from a lower energy principal energy level
  • Also less shielding makes the electron harder to remove
  • Successive ionisation energies give us evidence for principal energy levels
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5
Q

Ionisation Energy Across a Period

A

• Across a period, there is a general increase in the ionisation energies

  • The number of protons increase, so there is a stronger nuclear attraction
  • The shielding effect is similar as the outer electrons are at roughly the same energy level
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6
Q

Ionisation Energy Down a Group

A

• The first ionisation energy always decreases down a group

  • The nuclear charge increases down the group
  • But the electrons are being removed from successively higher principal energy levels, which are on average:
  • Further from the nucleus
  • More shielded by inner electron shells
  • And are therefore less attracted to the nucleus
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