Ionisation energy Flashcards
What is the definition of the first ionisation energy?
The energy required to remove one mole of electrons from one mole of gaseous atoms
Why is the first ionisation energy an endothermic process?
Energy is needed to overcome the electrostatic force of attraction between the negative electron and the positive nucleus
Write an equation for the second ionisation energy of calcium
Ca+ (g) –> Ca2+ (g) + e-
Write an equation for the third ionisation energy of aluminium
Al2+ (g) –> Al3+ (g) + e-
What 3 factors influence the ionisation energy?
Nuclear charge
Distance of electrons from the nucleus
Shielding effect
How does the nuclear charge influence the ionisation energy?
More protons = greater the nuclear charge
Nuclear charge is to do with number of protons in the nucleus of the atom
How does the distance of electrons from the nucleus influence the ionisation energy?
Nuclear attraction is reduced with increasing distance
Further the electron from the nucleus = easier it is to be remove
How does the shielding effect influence the ionisation energy?
Inner shell electrons repel the outer electrons
Repelling effect reduces attraction Experienced by the outer electrons from the nucleus
Electrons in the inner shells shield the outer electrons from the attractive force of the nucleus
Describe the trend in ionisation energy across a period
Nuclear charge increases
Outer electron in the same shell - atomic radius decreases
Shielding stays the same
Nuclear attraction increases
Electrons require more energy to remove
Ionisation energy increases across a period
Describe the trend in ionisation energy down a group
Nuclear charge increases - but is outweighed by the changes in shielding and shells
Outer electron in new shell - atomic radius increases
Shielding increases
Nuclear attraction decreases
Electrons requires less energy to remove
Ionisation energy decreases down a group
State and explain which element out carbon and nitrogen has the highest first ionisation energy
N has a higher nuclear charge that C
Outer electrons are in the same shell in C & N
Shielding stays the same
Atomic radius of N is smaller than C
Nuclear attraction on the outer electrons is higher in N
N has a greater first ionisation energy than C
Explain why boron has a lower first ionisation energy that beryllium
First electron in beryllium is removed from the 2s sub shell
First electron in boron is removed from the 2p sub shell
2p sub shell is higher energy than the 2s
Requires less energy to remove the first electron from boron than beryllium
Why does oxygen have a lower first ionisation energy than nitrogen?
Highest energy electrons are in the 2p sub shell
Oxygen has a pair of electrons in one p orbital which repel each other
Therefore, it’s easier to remove an electron from oxygen than nitrogen
How can electronic configurations of elements be predicted?
Successive ionisation energy data
What do successive ionisation energies provide?
Evidence for different energy levels
