Unit 3 Modern Atomic Theory Chpt 11 Modern Atomic Theory

Wave Mechanical Model Bohr’s atomic model only worked for 1 ELECTRON 1920s – quantum mechanics, or wave mechanical model develops Louis de Broglie proposed that electrons act as both waves and particles See demonstration

Electron probability Erwin Schrodinger proposes electron probability through wave function equations Where are you most likely to find e - ? Instead of orbits, electrons reside in orbitals, or 3D spaces around the nucleus Electron cloud around nucleus with fuzzy edges, no solid boundary

Uncertainty Principle Werner Heisenberg Uncertainty principle: the position and momentum of an electron cannot be found at the same time Momentum – lose position Position – shine light on it and excite e -

Principle energy level Principle energy level (n) – designates how close an e- is to nucleus, represented as number (1, 2, 3, …) Energy closest to nucleus is low and gradually gets higher e- are attracted to nucleus and require energy to remove that attraction Aufbau principle – electrons fill orbitals from lowest to highest energy level

Subshells Each princ energy level has subshells Subshell – the shape of the probability (orbital) of e- location  s,p,d,f s – 1 orbital p – 3 orbitals (p x,p y, p z ) d – 5 orbitals f – 7 orbitals Pauli exclusion principle – an orbital can hold a maximum of 2 electrons spinning in opposite directions

1s, 2s, 3s orbitals 2s2s

2p orbitals

d orbitals

f orbitals

Electron configuration To determine location of e-, use electron configuration Identifies number of electrons in ground state in each subshell at each energy level for that atom

Electron configuration To figure out how many subshells are in each energy level: 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p 7d

E- config examples H – 1 electron = 1s He – 2 electrons = 2s 2 Li – 1s 2 2s Be – 1s 2 2s 2 B – 1s 2 2s 2 2p C - 1s 2 2s 2 2p 2

Using the PT as a map

Orbital Box Diagrams Orbital box diagrams – illustrated representations of e- configuration Boxes = orbitals Arrows = electrons, demonstrates spin Electrons can only be paired in opposite directions H:

Hund’s Rule: To minimize repulsion and maintain low energy, electrons fill orbitals singly. When all orbitals are occupied by at least one e-, then electrons will pair up.

Shorthand e- configuration 1.Find the symbol for your element 2.Write the symbol in brackets for the noble gas at the far right of the proceeding horizontal row 3.Complete the rest of the e- config following that noble gas Ex: For magnesium: [Ne] 3s 2