Electrons Core electrons Valence electrons Energy Levels Electrons found in the inner shells Valence electrons Found in the outermost shell of an atom Energy Levels Each layer or shell is considered one energy level.

An element’s period number indicates the energy level of the element’s valence electrons.

Qwizdom Questions Which of the following elements have valence electrons in Energy Level 1? He B Si Which of the following elements have valence electrons in Energy Level 3?

Electron Configuration An electron’s “address” has four parts Energy level (1-7) Describes how far the electron is from the nucleus Energy sublevel (1s, 2s, 2p, 3s, 3p, 4s, 3d…) Describes what type of orbital an electron is in Contains one or more orbitals

Orbital (s,p,d,f) Describes the shape of space an electron occupies Can hold up to two electrons Superscript (1s1, 2p4, 4d8…) Indicates how many electrons are in each sublevel

# of Orbitals 1 3 5 7

Filling in Orbital Diagrams Find number of electrons Start adding electrons starting with first sublevel (1s) When a sublevel is completely filled, move on to next sublevel following the correct order Always add up arrow first. Once all orbitals in a sublevel have an up arrow, then you can add 2nd electron (down arrow)

Energy Level 1 H 1s1 He 1s2 Energy Level 2 Li 1s2 2s1 Be 1s2 2s2 B 1s2 2s2 2p1 C 1s2 2s2 2p2 N 1s2 2s2 2p3