Ionisation energy Flashcards
What is the definition of first ionisation energy?
The amount of energy required to remove one mole of electrons from on mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
What are the three factors that affect the first ionisation energy?
Atomic radius, nuclear charge and shielding.
How does atomic radius affect Ionisation energy?
The greater the distance between the nucleus and the outer electrons, the less the nuclear attraction. The force of attraction falls sharply with increasing distance.
How does nuclear charge affect ionisation energy?
The more protons that there are in the nucleus of an atom, the greater the attraction between the nucleus and the outer electrons
How does electron shielding affect ionisation energy?
Electrons are negatively charged and so inner-shell electrons repel outer-shell electrons. This repulsion reduces the attraction between the nucleus and the outer shell electrons.
Explain why the second ionisation energy of helium is greater than the first.
After the first electron is lost, the single electron is pulled closer to the Helium nucleus. The nuclear attraction on the remaining electron increases and more ionisation energy will be needed to remove the second electron.
What is the definition of the second ionisation energy?
The energy required to remove one electron from each atom in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions.
In a graph to show successive ionisation energies, what does a large difference in ionisation between two electrons show?
The large increase in ionisation energies suggests that the electron must be removed from a different shell, closer to the nucleus and with less shielding
Successive ionisation energies allow predictions to be made about three things. What are they?
The number of electrons in the outer shell, the group of the elements the periodic table, the identity of an element
What are the two main patterns in the graph below?
- A general increase in the first ionisation energy across each period (H → He, Li → Ne, Na → Ar)
- A sharp decrease in first ionisation energy between the end of one period and the start of the next period (He → Li, Ne → Na, Ar → K)
True or false? First ionisation energies decrease down a group.
True
Explain the trend in the first ionisation energy down a group. Include reference to atomic radius, number of inner shells, and general trend.
Explain the trend in the first ionisation energy across a period. Include reference to atomic radius and general trend.
