1 Chapter 7 Atomic Structure

2 The Periodic Table n Developed independently by German Julius Lothar Meyer and Russian Dmitri Mendeleev (1870”s) n Didn’t know much about atom. n Put in columns by similar properties. n Predicted properties of missing elements.

3 Aufbau Principle n Aufbau is German for building up n As the protons are added one by one, the electrons fill up hydrogen- like orbitals. n Fill up in order of energy

4 Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f 6f Orbitals available to a Hydrogen atom

5 Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f With more electrons, repulsion changes the energy of the orbitals.

6 Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f He with 2 electrons

7 Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f

8 Details n Valence electrons- the electrons in the outermost energy levels (not d). n Core electrons- the inner electrons n Hund’s Rule- The lowest energy configuration for an atom is the one have the maximum number of unpaired electrons in the orbital. n C 1s 2 2s 2 2p 2

9 Details n Elements in the same column have the same electron configuration. n Put in columns because of similar properties. n Similar properties because of electron configuration. n Noble gases have filled energy levels. n Transition metals are filling the d orbitals

10 The Shorthand n Write the symbol of the noble gas before the element n Then the rest of the electrons. n Aluminum - full configuration n 1s 2 2s 2 2p 6 3s 2 3p 1 n Ne is 1s 2 2s 2 2p 6 n so Al is [Ne] 3s 2 3p 1

11 The Shorthand Sn- 50 electrons The noble gas before it is Kr [ Kr ] Takes care of 36 Next 5s 2 5s 2 Then 4d 10 4d 10 Finally 5p 2 5p 2 [ Kr ]5s 2 4d 10 5p 2

12 Exceptions n Cr = [Ar] 4s 1 3d 5 n Mn = [Ar] 4s 2 3d 5 n Half filled orbitals n Scientists aren’t certain why it happens n same for Cu [Ar] 4s 1 3d 10

13 Formation of Ions n Metals ALWAYS gain electrons –Form cations (+) charge n Nonmetals ALWAYS lose electrons –Form anions (-) Charge

14 Formation of Ions Groups I and 2: Single ion formed is based on the number of “s” electrons Transition Metals: First Ion = # “s’ electrons Second = # “s” electrons + 1 P Sublevel Metals: First Ion = # “p” electrons Second Ion = # “p” + # “s” electrons