1.14 - Ionisation energies Flashcards
Where did the evidence for different energy levels initially come from?
Atomic emission spectra
What do electrons do when they return to their ground state?
Emit electromagnetic radiation of a specific wavelength
What instrument can we use to analyse EM radiation?
A spectroscope
What is unique for each element?
It’s emission spectrum
What do the fixed wavelengths of EM radiation being emitted show?
That electrons can only be in certain, fixed places
What is ionisation energy?
A measure of the energy required to completely remove an electron from an atom of an element
What is the general equation for the first ionisation energy of an atom?
A(g) -> A+(g) + e-
What is the general equation for the second ionisation energy of an atom?
A+(g) -> A2+(g) + e-
What two things are clear when you have a list of successive ionisation energies for an element?
- A steady increase in ionisation energy
- Big jumps in ionisation energies at certain points
Why is there a steady increase in ionisation energy as you remove more electrons?
- Once one electron is removed, the atom becomes a positive ion
- This means that the positive charge is greater than the negative charge
- So each electron feels a greater electrostatic force of attraction towards the nucleus
- Making it harder to remove each successive ion
- So the energy required to do so is greater
Why are there big jumps in ionisation energy for a specific element?
- The big jumps happen when an electron is being removed from a new shell
- This means that the inner shell is smaller
- So there is less shielding against the positive nucleus
- Meaning that the electrons in the outer shell feel a much greater force of attraction
- So a LOT more energy is required to remove them
What is the equation for Ionisation Energy?
IE = Energy of electron when removed - Energy of electron when in the orbital
