10.4 Energy Levels of Electrons Electrons move in definite energy levels; these are labeled Each level has sublevel(s) which are probability shapes that show where the electrons may be at any one time. Also known as orbitals. S orbital can hold up to 2 electrons (0, 1, 2) p orbital can hold up to 6 electrons (0-6) d orbital can hold up to 10 electrons (0-10) f orbital can hold up to 14 electrons (0-14) Aufbau chart shows how electrons fill into the main energy levels and the sublevels or orbitals

Energy Levels and Sublevels 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f

Aufbau Diagram or Chart 1s START HERE and follow 2s 2p the arrows! 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f

Electron Configuration 4 Be 1s 2 2s 2 15 P 1s 2 2s 2 2p 6 3s 2 3p 3 25 Mn 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5

Pauli Exclusion Principle Pauli exclusion principle states that no more than 2 electrons can be in the same suborbital. Even so, this would cause them to have precisely the same quantum address. So Pauli decided there has to be a way to tell one electron from another. In other words, they must differ by at least one quantum number!

Pauli Exclusion Principle So they invented spin (+1/2 or -1/2) called spin up and spin down. Has nothing to do with the direction of the electron--we don’ t know how they move just where they may be at with 90% chance of finding it inside the energy level and orbital designated.

Hund’s Rule Hund’s rule states that electrons fill unpaired until there is no more room then they will pair (applies to p, d and f orbitals)

Orbital Diagrams S orbitals get one box P orbitals get 3 boxes (2 e- per box) D orbitals get 5 boxes and f gets 7

Orbital Diagrams (cont.) Insert electrons (using arrows into each box according to Hund’s and Pauli) 2 p 3

Answer 2p 3 (arrows can all point up or down) Now try 4f 10

Answer to 4f 10 Arrows may point up or down if they are in boxes individually; however, if there are 2 electrons in a box, one must point up and one down.

Electrons and the Periodic Table Revisited History of the Table Periodic Law Important People

Mendeleev Mendeleev was a Russian chemist who arranged the known elements in vertical columns in order of increasing mass and noticed a pattern in physical and chemical properties

Mosley Mosley was a British physicist who determined the atomic number (number of protons) of the atoms of elements and then arranged the elements according to their atomic number.

Periods and Groups Periods of the periodic table are the rows across Groups or Families are columns on the periodic table. Currently we have 18 groups. We will use the 1-18 designations not the A/B or Roman Numerals

Areas of the Periodic Table Representative elements or Main Group are those that are in Groups 1, 2, 13, 14, 15, 16, 17, 18 Transition elements are Groups , also called the Heavy Metals

Inner Transition Rare Earth elements that are located in the bottom two rows (away from the rest of the table) of the periodic table

Periodic Table GROUP NUMBERS Heavy Metals or Transition elements Main group Main Group or Representative elements Inner Transition Elements Period Numbers

Groups with names Group 1 = Alkali Metals Group 2 = Alkaline Earth Metals Group 18 = Inert or Noble Gases Group 17 = Halogens

Periodic Table and Electron Configuration The light metals compose the s block. The transition elements are the d block. The nonmetals are p block. The inner transition (rare earth) metals are the f block.

Periodic Table f 5f s block d block p block f block Noble (inert) gases

Complete the electron configurations for the Noble Gases (Hint: Group 18) He 1s 2 Ne 1s 2 2s 2 2p 6 Ar = 1s 2 2s 2 2p 6 3s 2 3p 6 Kr = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1 0 4p 6 Xe = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 Rn = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 1 0 6p 6 Except He, do you see a trend in all of the noble gas configurations? What do they all end in?

Shorthand Notation We use the noble gases in shorthand notation Find the closest noble gas that has an atomic number LESS than that of the element

Example Ex. K What is K’s atomic number? 19 Closest noble gas? Ar What is Ar’s atomic number? 18 = 1s 2 2s 2 2p 6 3s 2 3p 6 = [Ar] 4s 1 = Means the first 18 electrons are arranged like argon and the last electron is called the VALENCE ELECTRON (outermost shell)

Example for you to try You try Ba Ba = [Xe] 6s 2 Try Pb Pb = [Xe] 6s 2 4f 14 5d 10 6p 2