The Bohr Model of the Atom Bohr’s major idea: The energy of the atom is quantized, which is related to the electron’s position in the atom quantized means that the atom could only have very specific amounts of energy

The Bohr Model of the Atom Electron Orbits in the Bohr Model, electrons travel in orbits around the nucleus more like shells than planet orbits the farther the electron is from the nucleus the more energy it has. n Energy level.

The Quantum-Mechanical Model of the Atom Erwin Schrödinger predicts the probability of finding an electron with a particular amount of energy at a particular location in the atom

The Quantum-Mechanical Model Orbitals: (Erwin Schrödinger ) An orbital is a region where we have a very high probability of finding the electron when it has a particular amount of energy. generally set at 90 or 95%

Probability Maps & Orbital Shape “s” Orbitals There is only one “s” Orbital (in each energy sub-level.

Probability Maps & Orbital Shape “p” Orbitals The p sublevel contains 3 orbitals, all with the same dumbbell-like shape

Probability Maps & Orbital Shape “d” Orbitals: The d sublevel contains 5 orbitals.

Probability Maps & Orbital Shape “f” Orbitals The f sublevel contains 7 orbitals.

Orbitals in each sublevel: Shells & subshells: Orbitals in each sublevel: 1 3 5 7 Maximum # of electrons: 2 6 10 14

Electrons enter the lowest energy level first. Aufbau Principle: Electrons enter the lowest energy level first. 1s 2s 2p 3s 3p 4s 1st Energy level 2nd Energy level 3srd Energy level 4th Energy level

Pauli Exclusion Principle: An atomic orbital may describe two electrons. (No more than two electrons are admitted in each atomic orbital) Example: One electron Z=5 2p1 1s 2s 2p 3s 3p 4s 2 2 1 2nd Energy level Sublevel “p”

Examples: Na (Z=11) Mg (Z=12) Al (Z=13) Si (Z=14) Ne (Z=10) 1s2 2s2 2p6 3s2 3p1 1s2 2s2 2p6 3s2 3p2 1s2 2s2 2p6

Pauli Exclusion Principle: The two electrons in each orbital have opposite spin (spin is a quantum number that indicates the direction in which an electron moves). Arrows are use to represent the electron and direction in an orbital diagram: Orbital filling diagram: 2s 2p 2p 2p

When electrons occupy orbitals of equal energy, one electron enters each orbital until all of them contain one electron with parallel spin, then the second electron is added to each orbital so their pair the spin. Hund’s Rule:

1s2 2s2 2px2 2py1 2pz1 Ground-State configuration: Z=8 Orbital filling diagram: 1s 2s 2px 2py 2pz 1s2 2s2 2p4 Then, ground-state configuration applying the Hund’s Rule: 1s2 2s2 2px2 2py1 2pz1

Examples: Si (Z=14) S (Z=16) 3px1 3py1 1s2 2s2 2p6 3s2 3px2 3py1 3pz1

Noble - gas notation: Use the bracketed symbol of the nearest preceding noble gas in the Periodic Table. It allows you to represent the complete electron configuration in a shorthand form. Examples:

Na (Z=11) N (Z=7) Ca (Z=20) 1s2 2s2 3s2 4s2 Noble-Gas Notation: 3s1 [Ne] 3s1 1s2 2s2 2p6 3s1 [He] 2s2 2p3 1s2 2s2 2p3 1s2 2s2 2p6 3s2 3p6 4s2 [Ar] 4s2

Electron-Dots Structure: The electrons in the outermost energy level are represented as dots around the element symbol: Al [Ne] 3s2 3p1 Si [Ne] 3s2 3p2 P [Ne] 3s2 3p3

Electron – dots structure: The element’s symbol represent the atom’s nucleus & inner levels electrons. The dots represent the valence electrons (electrons in the outermost energy level).

Z=16 (16 electrons must be distributed) 1) Ground State Configuration: Review: Z=16 (16 electrons must be distributed) 1) Ground State Configuration: 2) Applying the Hund’s Rule: (Two unpaired electrons) 3) Noble-Gas Notation: 4) Noble-Gas Notation & Hund’s Rule: 1s2 2s2 2p6 3s2 3p4 1s2 2s2 2p6 3s2 3px2 3py1 3pz1 [Ne] 3s2 3p4 [Ne] 3s2 3px2 3py 1 3pz1

5) Orbital filling diagram: [Ne] 3s2 3p4 3s 3px 3py 3pz 6) Electron-Dot Structure: S 7) How many valence electrons it has? 6

P Practice: 1) Ground State Configuration: 2) Orbital filling diagram: 3) Applying the Hund’s Rule: 4) Noble-Gas Notation & Hund’s Rule: 5) Electron-dots: Z = 15 1s2 2s2 2p6 3s2 3p3 3s 3px 3py 3pz 1s2 2s2 2p6 3s2 3px1 3py1 3pz1 [Ne] 3s2 3p3 [Ne] 3s2 3px1 3py1 3pz1 P Valence e- : 5