Electronic Structure of the Atom Electrons  Bonding  Properties

Bohr ’ s Model Proposed that electrons in a H-atom could only exist in specific energy states. Electrons could move from one orbit to another by absorbing or emitting specific amounts of energy called a “ QUANTUM ”, corresponding to the energy differences between the orbits.

THEORY OF QUANTUM MECHANICS Electrons occupy particular regions of space called ORBITALS, in a particular energy level.

Energy Level Diagram for H (Hebden pg 152) Quantum Number = n

Orbital For each orbital, the maximum number of electrons you can have is 2!

Analogy Pauli Exclusion Principle Bus scenario: You only sit with someone (seats for 2 occupants) when there are no other seats left. Fill up the same energy level first with 1 electron, before you pair it up with the 2 nd electron

Analogy Analogy: Filling a bottle of jam  Fills up the bottom (representing the lower energy) before moving higher up the bottle (the next higher energy level) Fill up the lower energy shells first before you move up to the next higher energy level

Definitions Shell = the set of all orbitals all having the same n-value. Eg. 3 rd shell consists of 3s, 3p, 3d orbitals Subshell = a set of orbitals of the same type Eg. The set of five 3d-orbitals is a subshell

Rules: Types of Orbitals Possible n = 1Only s n = 2s and p n = 3s, p and d n = 4s, p, d and f

Rules: Orbitals SubshellNo. of Orbitals Max. No. of e s-type1 s-orbital1X2 = 2 p-type3 p-orbitals3X2 = 6 d-type5 d-orbitals5X2 = 10 f-type7 f-orbitals7X2 = 14

Orbital Shapes (Do NOT memorize, this is extra info)

Problem … The energy level diagram Bohr had only worked for H, 1 electron... What about polyelectronic atoms?

Energy Level Diagram for Polyelectronic Atoms (Hebden pg 153)

Electronic Configuration A description of how the electrons of an atom are arranged into orbitals.

Electronic Configuration: 2 Rules You MUST know!! 1)Electrons are added to the orbitals having the LOWEST energy first. The order in which orbitals are filled is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p … (Do not memorize these energy levels! Just fill up your subshells by following their orders in the periodic table  Next Slide “ Subshells in the Periodic Table ” ) 2) A maximum of 2 e can be placed in each orbital. This means there can be a maximum of 2e in s-type subshell, 6e in p-type subshell, 10e in d-type subshell, 14e in f-type subshell

Subshells in the Periodic Table (Hebden pg 155)

Practice Problems: Write Electronic Configuration for the following (a)He (b)Li (c)O (d)Cl

Homework Hebden Unit VIII: Do Question 26 (a) to (o) (pg 155)