F321: Electron Structure

Shell Number               Maximum number of electrons
        1                                         TWO
        2                                        EIGHT
        3                                     EIGHTEEN
        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.