Electrons are grouped in different energylevels, called electron shells, each labelled with the number n = 1, 2, 3,…, with n = 1 being the closest to the nucleus
1. Heating an element can cause an electron to absorb energy and jump to a higher energy level (excited state)
2. Shortly after, as its energy decreases, the electron returns to the lower energy level, releasing a fixed amount of energy as light (the difference between the 2 energy levels)
3. Each transition corresponds to a specific energy of light and thus, one line in the line spectrum for that element
The energy needed to remove an electron from an atom (the first electron to be removed has the lowest ionisation energy and thus, is the easiest to remove)
Every orbital in a subshell must first be filled with one electron with the same spin before an orbital is filled with a secondelectron of opposite spin