Shell Number Maximum number of electrons
4 THIRTY TWO
An atomic orbital is a region within an atom which can hold up to two electrons with opposite spin.
S-Orbital shape = Sphere P-Orbital shape = A dumbbell shape
Subshell Subshells present Number of orbitals in each subshell Total number of electrons
1 s 2 2
2 s,p 2,6 8
3 s,p,d 2,6,10 18
Sub shells and electrons fill up lowest energy level first, singly before they pair up.
e.g. Calcium = 1s2 2s2 2p6 3s2 3p6 4s2 (4s before 3d)
Across A Period
-General increase across the period.
-There are more protons in the nucleus, so greater charge.
-Outer electrons in same shell.
-Increased nuclear attraction.
-Held more closely and require more energy.
Down A Group
-General decrease down group.
-More electron shells so the outer electrons are further away (bigger atomic radii).
-More shielding, which repel more.
-Number of protons increase, but is outweighed.
-Held less tightly, require less energy.
Succesive ionisation energies are a measure of the energy required to remove each electron from an atom.
Ionisation energy is the energy required to remove an electron from all atoms in a mole of a gaseous substance.