Expanding the Theory of the Atom Chapter 7

Energy levels and Sublevels We already know that electrons occupy energy levels-regions in space around the nucleus There are also sublevels – divisions within an energy level – identified as s, p, d, or f

Energy Levels and Sublevels (con’d) The order of sublevels from lowest to highest energy is s, p, d, f 1st energy level has 1 sublevel -1s 2nd has 2 sublevels – 2s, 2p 3rd has 3 – 3s, 3p, 3d 4th has 4 - 4s, 4p, 4d, 4f So within the 4th energy level the 4s is the lowest energy, and the 4 f is the highest

Sublevels Just as energy levels have a maximum number of electrons they can hold, so do sublevels An s sublevel can hold 2 e- P can hold 6 D can hold 10 F can hold 14

Heisenberg A scientist named Werner Heisenberg concluded it is impossible to accurately measure both the location and energy of an electron at the same time – the Heisenberg uncertainty principle. Relates to the electron cloud model (p. 239)

Orbitals Sublevels are further divided into orbitals. An orbital can hold a maximum of 2 e- The s sublevel has 1 orbital (2 e- max) P has 3 orbitals (6 e- max) D has 5 orbitals (10 max) F has 7 orbitals ( 14 max) Diagrams p. 239

Electron Configuration In an atom electrons are distributed among the energy levels, sublevels, and orbitals in the way that creates the most stable arrangement – the lowest energy This most stable arrangement of electrons in sublevels and orbitals is called electron configuration.

Electron configuration (con’d) Electrons fill orbitals and sublevels from the innermost (closest to the nucleus) to the outermost (furthest from the nucleus)

Helpful diagram for Electron Configuration (Con’d)

Helpful diagram for Electron Configuration (Con’d)

When Doing an Electron Configuration Figure out how many electrons are in the atom you are trying to figure out Fill electron into lower energy levels first Follow order of filling Remember how many electrons each level can hold: s holds 2, p holds 6, d 10, f 14

When Doing an Electron Configuration (Con’d) Write the configuration in this format Energy Level (number), sublevel(letter), Number of electrons in that sublevel (superscript) Ex: 1s2 2s2 2p1

Shorthand (noble gas) notation Shows the electron filling starting from the previous noble gas. Ex: P: [Ne] 3s2 3p3

Lets Try Some