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Ch 8 electron configuration

# Ch 8 electron configuration - Ch 8 Periodic Properties of...

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Ch 8. Periodic Properties of Elements A. 8.3 Electron configuration = notation to show the distribution of electrons into the orbitals of a ground state atom (the particular orbitals that are occupied for that atom) a.i. the number is n ; the letter is l ; the superscript is the number of electrons in that sublevel a.ii. example) Lithium: a.ii.1. full electron configuration: 1s 2 2s 1 a.ii.2. or can use noble gas abbreviation: [He] 2s 1 b. ground state : lowest energy state; lowest energy orbitals possible c. electrons organized in logical manner; as atomic # increases, e- are added to subshells acc to their energy c.i. lower energy subshells fill b4 higher energy subshells (two in each) c.ii. order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p d. orbital diagram : electrons drawn as arrows, orbitals as boxes; provides same info as electron configurations d.i. arrow directions represent electron spin (always opposite spin) d.ii. orbitals can hold 0-2 electrons only d.iii. how to fill in electrons: d.iii.1. add one electron to each box in a subshell , then PAIR the electrons before going on to next set of subshells; (for pairs draw opposing arrows) d.iii.2. if electrons had the choice, they’d all rather have their own orbital (in same subshell) e. electron spin + Pauli Exclusion Principle e.i. electron spin – designated by direction of half-arrow, pointing up or down e.i.1. spin = basic property—all electrons have the same amount of spin e.i.2. orientation of spin is quantized, w/ only 2 possibilities of spin up and spin down e.i.2.a. spin of electron= 4 th quantum number ( spin quantum number m s ) e.i.3. possible values: + (spin up) or (spin down)

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f. Pauli exclusion principle : no two electrons in an atom can have the same four quantum numbers f.i. b/c 2 electrons occupying same orbital have 3 identical quantum numbers ( n, l, m l ) , they must have diff spin numbers f.ii. basically: each orbital can have a maximum of only 2 electrons w/ opposing spins g. Sublevel Energy Splitting in Multielectron Atoms g.i. for hydrogen : the sublevels in each principal energy level are degenerate (have the same energy) g.i.1. ns = np = nd = nf g.i.1.a. degenerate = same energy g.ii. for multielectron atoms , the energies of the sublevels are split due to electron-electron repulsion; the lower the value of the l , the lower the sublevel’s energy g.ii.1. ns < np< nd < nf g.ii.2. this is due to 3 things: g.ii.2.a. Coulomb’s law : PE of 2 charged particles depends on charges + separation g.ii.2.b. shielding : the repulsion of one electron by other electrons so electron doesn’t feel full effects of nuclear charge g.ii.2.b.i. effective nuclear charge (Z
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Ch 8 electron configuration - Ch 8 Periodic Properties of...

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