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Rules and examples for writing electron configurations for neutral atoms and ions. It explains the concept of core and outer electrons, and provides exceptions for certain elements. Students are encouraged to create a table for elements p, ti, co, br, sr, ar, k, cd, ca, xe, cs, pb, ga, mn, and zr.
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Chem 11 Electron Configuration Notes
2 simple rules;
Electron Configuration : is a description of which orbitals in an atom contain electrons and how many electrons are in each orbital.
2 e-^ 10 e-^ 6 e-
Fill the electron from the lowest energy level first then continue filling until all electrons have been placed. If unsure refer to the above orbital version of the periodic table and simply fill electrons.
Notice that 4s fills before 3d, which fills before 4p orbital – refer to the periodic table above.
example H = (1s^1 ) He = (1s^2 ) Li = ( 1s^2 2s^1 ) Be = (1s^2 2s^2 ) B = (1s^2 2s^2 2p^1 ) O = (1s^2 2s^2 2p^4 ) F = (1s^2 2s^2 2p^5 ) Ne = (1s^2 2s^2 2p^6 ) Fe = (1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6 ) Se = (1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^4 )
The set of electrons belonging to a given atom can be divided into two subsets: the CORE electrons and the OUTER electrons. core : of an atom is the set of electrons having the configuration of the nearest noble gas (He, Ne, Ar, Kr, etc.) having an atomic number less than that of the atom being considered.
Rules:
There are two exceptions to the configuration of elements up to Kr.
Expect Cr ([Ar] 4s^2 3d^4 )
Right WAY Cr ([Ar] 4s^1 3d^5 )
Expect Cu ([Ar] 4s^2 3d^9 )
Right WAY Cu ([Ar] 4s^1 3d^10 )
On a separate sheet of paper make a 3 column table and label
Element Full Notation Core Notation P Ti
Then write out the notation for the following elements;