Bohr Model Diagrams of atoms Part 3 of Atomic Structure Bromine atom…needs one electron to have an octet in outer shell Krypton atom…very stable and nonreactive because it has a full octet

Special Family Names on the Periodic Table Alkali Metals = hot orange Semimetals/Metalloids = pink Alkaline Earth Metals = Faded Blue Halogens = Yellow Transition Metals = Indigo Noble Gases = Pumpkin Orange Other Metals = Baby Blue Other Nonmetals = Green

ATOMIC STRUCTURE Electrons are arranged in Energy Levels or Shells around the nucleus of an atom. first shell a maximum of 2 electrons second shell a maximum of 8 electrons third shell a maximum of 8 electrons 3

Electrons in larger shells have higher energy levels 1st shell (corresponds to period 1 on periodic table): lowest energy level 2nd shell (period 2) 3rd shell (period 3) …. 7th shell (period 7): highest energy level

Drawing Bohr Model Diagrams You must know the # of protons, neutrons, and electrons Draw protons (p+), (n0) in circle (i.e. “nucleus”) Draw the number of energy levels or shells needed (the same as the period it is found in) Draw dots for electrons into the shells (order of filling is 2,8,8,2 for the first 20 elements He Li 3 p+ 4 n0 2e– 1e– Li shorthand 3 p+ 4 n0 2 p+ 2 n0 Draw Be, B, Al and shorthand diagrams for O, Na

Be B Al O Na 8 p+ 11 p+ 8 n° 12 n° 4 p+ 5 n° 5 p+ 6 n° 13 p+ 14 n° 2e– 8e– 1e– Na 8 p+ 8 n° 2e– 6e– O

1. Bohr Models: nucleus and concentric rings ATOMIC STRUCTURE There are at least two ways to represent the electron arrangement of an element or compound; 1. Bohr Models: nucleus and concentric rings 2. Electron Configuration: summary of # of electrons in each shell like 2,8,8, 1 for potassium (K) 7

ELECTRONIC CONFIGURATION Write the electronic configuration for the following elements; 40 23 16 Na O Ca a) b) c) 8 11 20 2,8,8,2 2,8,1 2,6 35 28 11 Cl Si B d) e) f) 5 17 14 2,8,7 2,8,4 2,3 8

SUMMARY The Atomic Number of an atom = number of protons in the nucleus. The Atomic Mass of an atom = number of Protons + Neutrons in the nucleus. The number of Protons = Number of Electrons. Electrons orbit the nucleus in shells. Each shell can only carry a set number of electrons. 9