Do Now Take out flame test lab. Work on post lab questions part 2 (2nd page)—turn in Unit 6/7 Test TUES 11/17!

Electrons and Orbitals Although the Bohr Model (Planetary Model or Electron-Shell Model) is a useful way of picturing electrons and their transitions between ground and excited state, electrons don’t actually travel around the nucleus in circular orbits! Schrodinger, deBroglie and Heisenberg developed quantum mechanics in the 1920’s to explain the movement of electrons

Electrons move in random paths, like bees moving around a hive. THE ELECTRON CLOUD Electrons move in random paths, like bees moving around a hive. This idea was proposed by Erwin Schrodinger. An orbital is defined as a 3-D region of space surrounding the atomic nucleus where an electron with a given energy is most likely to be found.

THE ELECTRON CLOUD According to the current model of the atom, electrons are located in an electron cloud, which is called an orbital An orbital is 3-D REGION in space in which there is a high chance of finding an electron

S-orbitals s-orbitals are spherical and can contain a maximum of 2 electrons.

P-orbitals p-orbitals are shaped like dumb-bells and are situated on each of the three axes (x, y, z). A total of 6 electrons can fit in the p-orbitals: 2 electrons in px 2 electrons in py 2 electrons in pz http://www.chemistry.uvic.ca/chem222/Notes/lect3v1.htm

D-orbitals There are five arrangements, known as spatial orientations, of d-orbitals, holding a total of 10 electrons.

F-orbitals f-orbitals have seven possible arrangements; each orbital holds two electrons for a total of 14 electrons in f-orbitals.

ORBITALS In every atom, even if the shells are not full, they still exist and overlap.

Aufbau Principle Under normal conditions, each electron occupies the lowest energy orbital available. http://www.iun.edu/~cpanhd/C101webnotes/modern-atomic-theory/aufbau-principle.html

Pauli Exclusion Principle Every electron spins; it can spin in one of two directions. An arrow pointing up (↑) indicates one direction. An arrow pointing down (↓) indicates the other direction. The Pauli exclusion principle states that a maximum of two electrons (an electron pair) can occupy an orbital space, but only if they have opposing spins. OR RIGHT WRONG

Hund’s Rule WRONG RIGHT To minimize repulsion between electrons, Hund’s rule says that we put one electron in each orbital of the same energy before we add the second. p subshell WRONG RIGHT Room mate rule

Electron Configuration: 3 parts # electrons in orbital Energy Level Type of orbital

Valence Electrons The electrons in the outermost shell or highest energy level Valence electrons = total number of electrons in the highest s and p orbitals (must be of the same energy level)!

Noble Gases: Group 18 Have octet=full valence (outermost) shell All elements want to be a noble gas (so freaking bad). In other words, all elements want to have a full valence shell Remember: “8 IS GREAT!” Exception: helium: it only has 2 valence electrons

2 2 4

Electron Configurations can get very long! A shortened form of the electron configuration can be written for most elements. This shortened form is referred to as the noble gas abbreviated electron configuration, or short form. Beryllium: [He] 2s2 2 valence electrons