Periodic Table and Configuration

Demetri Mendeleev Created modern periodic table (late 1800’s) Arranged by increasing atomic mass Similar elements found in columns

Modern Table Elements are in columns called groups or families All elements within a group have similar chemical properties and can often be used to replace one another in compounds to produce new compounds with slightly different properties Horizontal rows are called periods

Three Distinct Regions Representative elements are chemically active elements Transitional metals are in center of the table Inner transitional metals are the two rows below 1) top row called lanthanides 2) bottom row called actinides

Group Names Group 1 – Alkali Metals Group 2 – Alkaline Earth Metals Group 16 – Chalcogens Group 17 – Halogens Group 18 – Noble or Inert Gases

Metallic Character Elements can also be divided by metallic character Metalloid – between metal and non-metal

Configuration Arrangement of electrons in the atom Aufbau Principle – orbitals fill in order of increasing energy

Orbital Diagram of Li ( 3 e-) 1s 2 2s 1

Orbital Diagram of B (5 e-) 1s 2 2s 2 2p 1

Hund’s Rule Electrons occupy degenerate orbitals singly first

Orbital Diagram of C (6 e-) 1s 2 2s 2 2p 2

Orbital Diagram of Ne (10 e-) Configuration 1s 2 2s 2 2p 6

Example Determine the configuration of Fe Br

Magnetism When electrons in half-filled degenerate orbitals spin in the same direction, the material is magnetic

Valence Electrons Outer shell electrons Ones in the last main energy level ▪ K 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 1 valence e Fe 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 2 valence e