Atomic Structure Flashcards
Define ‘Ionisation Energy’
The amount of energy needed to remove one mole of electrons from mole of gaseous atoms (to form one mole of +1 gaseous ions)
Why is the first ionisation energy of boron lower than the first ionisation energy of beryllium?
Boron’s outermost electron is from a higher energy orbital /sub-shell than beryllium’s outermost electron, so the nucleus exerts less attractive forces on it.
Why is the first ionisation energy of oxygen lower than the first ionisation energy of nitrogen
Oxygen’s outermost electron is in an orbital that contains two electrons. Repulsion between the paired electrons reduces the amount of energy needed to remove the outermost electron
Why is the first ionisation energy of aluminium lower than the first ionisation of magnesium?
The outermost electron of aluminium is located on a higher energy sub-shell than magnesium, so less energy is needed to remove it.
Why is the first ionisation energy of sulphur lower than the first ionisation energy of phosphorus?
The outermost electron of sulphur is in a sub-shell containing two electrons. As the electron are both negatively charged they repel each other, so less energy is needed to remove the outermost electron.
How does increasing atomic radius affect ionisation energy?
Increasing atomic radius reduces ionisation energy. As valence electrons get further from the nucleus, the forces of attraction between them decreases, and less energy is required to remove the valence electrons.
How does increasing nuclear charge affect ionisation energy?
Increasing nuclear charge increases ionisation energy. As nuclear charge increases the force of attraction between the nucleus and valence electrons increases, and more energy is required to remove electrons.
How does increasing electron shielding affect ionisation energy
Increasing electron shielding reduces ionisation energy. As the amount of inner electrons shells increases in an atom, there is a larger shielding effect on the outer electrons’ attraction to the nucleus. Therefore, less energy is needed to remove them.
How does ionisation energy change across a period?
Ionisation energy increases across a period
Across a period, nuclear charge increases with number of protons, increasing the attraction of electrons to the nucleus. This also means that atomic radius decreases. As a result, the energy needed to remove the outermost electrons increases.
Furthermore, electron shielding remains constant across a period
How does ionisation energy change going down a group?
Ionisation energy decreases going down a group
As number of inner electron shells increases, atomic radius increases. Electron shielding also increases, reducing forces of attraction between the nucleus and electrons. The increase in electron shielding outweighs the increases nuclear charge resultant of increasing number of protons. Thus, less energy is required to remove the outermost electrons.
