# 2 the period number is the n value of the highest

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2. The period number is the n value of the highest energy level. 3. The n value squared ( n 2 ) gives the total number of orbitals and 2 n 2 gives the maximum number of electrons in the energy level. 66
Take them (electrons) out rule We form cations from elements when we remove the electrons from the highest n first . If sub-shells exist within the highest n then first take the electrons from the highest “ l ”. Examples: Write electron configurations for Mn +2 and Ge +2 67
Take them out rule To form cations from elements remove the electrons from the highest n first . If sub-shells exist within the highest n then first take the electrons from the highest “ l . Examples: First write electron configuration for Mn: [Ar] 3d 5 4s 2 68
Take them out rule To form cations from elements remove the electrons from the highest n first. If sub-shells exist within the highest n then first take the electrons from the highest “ l ”. Examples: First write electron configuration for Mn: [Ar] 3d 5 4s 2 Then take out electrons as directed to get Mn +2 : [Ar] 3d 5 By the way how many unpaired electron does this ion have? 69
Take them out rule To form cations from elements remove the electrons from the highest n first. If sub-shells exist within the highest n then first take the electrons from the highest “ l ”. Examples: First write electron configuration for Ge: 70
Take them out rule To form cations from elements remove the electrons from the highest n first. If sub-shells exist within the highest n then first take the electrons from the highest “ l ”. Examples: First write electron configuration for Ge: [Ar] 3d 10 4 s 2 4 p 2 71
Take them out rule To form cations from elements remove the electrons from the highest n first. If sub-shells exist within the highest n then first take the electrons from the highest “ l ”. Examples: First write electron configuration for Ge: [Ar] 3d 10 4s 2 4p 2 Then take out electrons as directed to get Ge +2 : [Ar] 3d 10 4s 2 By the way how many unpaired electron does this ion have? 72
Take them out rule To form cations from elements remove the electrons from the highest n first. If sub- shells exist within the highest n then first take the electrons from the highest “ l ”. Examples: First write electron configurations for Ge: [Ar] 3d 10 4s 2 4p 2 Ge +2 : [Ar] 3d 10 4s 2 73
Splitting of Levels into Sublevels Each energy level is split into sublevels of differing energy. Splitting is caused by penetration and its effect on shielding. For a given n value, a lower l value indicates a lower energy sublevel. Order of sublevel energies: s < p < d < f 74
Period 4 crossover in sublevel energies Because the 4s electron penetrates closer to the nucleus, the energy of the 4s orbital is lower in K and Ca; thus, the 4s fills before the 3d.