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Description
Flashcards by Iqra Rashid, updated more than 1 year ago
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Created by Iqra Rashid
over 8 years ago
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| Question | Answer |
| What is the definition of ionisation energy? | The energy required to remove a mole of electrons from a mole of ions in the gaseous state measured in kJmol-1. |
| What is the general equation for ionisation energy? | X(g) --> X+(g) + 1e- |
| How are we able to measure ionisation energy? | We remove an electron from the outer shell, moving towards the nucleus, and measure how much energy is released. |
| What is the difference between ionisation energy and electron affinity? | The energy change for the formation of a positive ion is called the ionisation energy, but the energy change for the formation of a negative ion is called the electron affinity. |
| What does the term successive ionisation energies mean? | The increase in energy needed to remove electrons the closer you get to the nucleus. The equations are as follows: |
| What are the three factors we need to consider to explain trends in ionisation energies? | o Size of nuclear charge o Atomic radius o Electron shielding |
| How does the size of the nuclear charge affect ionisation energy? | Protons in the nucleus attract the outer electrons. To remove and electron requires the input of energy, ionisation energy, to overcome the attractive force. The greater the attraction, the greater the ionisation energy. |
| How does atomic radius affect ionisation energy? | The attractive force of the protons on the outer electrons decreases with distance. The greater the atomic radius, the lower the ionisation energy. |
| How does electron shielding affect ionisation energy? | In most atoms, between the outer electron and the nucleus, there will be other electrons in lower energy levels. These will repel the outer electron, decreasing the attractive forces between the outer electron and the nucleus. The greater the shielding, the lower the ionisation energy. |
| General trends down a group: Ionisation energy levels decrease down a group. | Be: 1s2 2s2 Mg: 1s2 2s2 2p6 3s2 Ca: 1s2 2s2 2p6 3s2 3p6 4s2 1) Nuclear energy increases-IE increases 2)atomic radius increases-IE decreases 3) electron shielding increases-IE decreases |
| General trends across a period: Ionisation energy levels increase across a period | Li: 1s2 2s1 Be: 1s2 2s2 B:1s2 2s2 2p1 1) Nuclear charge increase-IE increases 2) Atomic radius has a slight increase-little effect on IE 3) Shielding remains the same-little effect on IE |
| Evidence for sub levels (Al) | The first ionisation energies for period 3 shows a general increase. However, Aluminium's value is below that of magnesium. This is because the outer shell electron is in the 3p orbital, which is of a slightly higher energy level than the 3s subshell, therefore requiring less energy to remove it. |
| Evidence for subshells (S) | In sulphur, one of the 3p orbitals contains 2 paired electrons while in phosphorous each of the orbitals contains only one electron. The repulsion between these paired electrons makes it easier to remove one of them despite the increase in nuclear charge. |
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