Electrons Core electrons 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 1. Which of the following elements have valence electrons in Energy Level 1? a. He b. B c. Si 2. Which of the following elements have valence electrons in Energy Level 3? a. He b. B c. Si

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

3. Orbital (s,p,d,f) Describes the shape of space an electron occupies Can hold up to two electrons 4. Superscript (1s 1, 2p 4, 4d 8 …) Indicates how many electrons are in each sublevel

# of Orbitals

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 2 nd electron (down arrow)

Energy Level 1 H1s 1 He1s 2 Energy Level 2Li1s 2 2s 1 Be1s 2 2s 2 B 1s 2 2s 2 2p 1 C1s 2 2s 2 2p 2 N1s 2 2s 2 2p 3