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What is the genreal equation for first ionisation energy?
X(g) → X+(g) + e-
How does nuclear charge affect ionisation energy?
The more protons there are, the greater the nuclear charge
This provides a greater attraction for the electrons
This increases ionisation energy
How does distance affect ionisation energy?
Attraction falls away quickly with distance
Ionisation energy decreases as distance increases
How does shileding affect the ionisation energy?
As the number of electrons between the outer electrons and the nucleus increases, the less attraction the outer electrons feel
What is the overall trend in ionisation energy across period 3?
Increases
Nuclear charge increases as the number of protons increases
All electrons are in the same principle energy level so shielding is similar and the distance is the same
What is the overall trend of ionisation energy going down group 2?
Decreases
Distance and shielding increases
The attraction is weaker as you go down the group so less energy is required to remove the electrons
What is the first ionisation energy?
The energy required to remove 1 electron from each atom in 1 mole of gaseous atom to form 1 mole of gaseous ions
What are the exceptions in the trend going across period 3?
Slight decrease between Mg and Al as the highest energy electron is in a 3p subshell so it is slightly more shielded
Slight decrease between P and S because sulfur has a pair of electrons that repel each other in an orbital which makes it easier to remove an electron
Why is ionisation energy endothermic?
Energy is required to overcome the attraction between the negative electron and positive nucleus
