The Periodic Table

What Does Periodic Mean? Periodic means repeated in a pattern Think about a calendar: Weeks are periodic – they repeat every 7 days

Dimitri Mendeleev (1834 - 1907) Created the first way to organize all known elements Based his table on the pattern of chemical properties

Mendeleev’s Periodic Table Based on chemical properties Organized by atomic masses Predicted unknown elements

Henry Moseley (1887 – 1915) His work led to a reorganization of Mendeleev’s table by atomic number Killed by a sniper in World War One at age 27

The Modern Periodic Table Organized into Rows = Periods Columns = Families

Periods and Families The families are numbered at the top of your periodic table in your reference table Take a pen and number the periods Number one is the row with Hydrogen Number seven is the row with Francium

Names of Families Group 1A or 1 Alkali Metals

Names of Families Group 2A or 2 Alkaline Earth Metals

Names of Families Group 7A or 17 Halogens

Names of Families Group 8A or 18 Noble Gasses

Special Groups Groups 3-12 Transition Metals

Special Groups 1st Row at Bottom Lanthanoids OR Lanthanides

Special Groups 2nd Row at Bottom Actinoids OR Actinides

One Other Feature Notice the dark stairstep line. Separates metals from nonmetals

Metals To the left of the stair-step line Typically solids with high melting points Good conductors of heat and electricity Malleable – can be formed into a different shape Ductile – can be drawn into wires

Metals As you move left across the periodic table, metals become more reactive As you move down a group (family), metals become more reactive Remember the video about cesium? Where are the most reactive elements on the periodic table?

Metalloids Touching the stair-step line Have properties in between metals and nonmetals Semiconductors – Think silicon in computer chips

Nonmetals To the right of the stair-step line Typically gasses with low melting points Very poor conductors of heat and electricity Brittle – break rather than change shape

Nonmetals As you move right across the periodic table, nonmetals become more reactive As you move down a group (family), nonmetals become less reactive Where are the most reactive nonmetals?

Exit Ticket On the index card, please answer the following questions: Which group is the halogens? What is the most reactive non-metal? What is the most reactive metal? List two metalloids.