Periodic Table of Elements

What is an element? Element - a pure substance that cannot be broken down into simpler substances In other words, made up of only one kind of atom Elements can be divided into: Metals Non-metals Metalloids

Each element has its own symbol ONLY two letters long (normally) Starts with a capital and ends with a lowercase

Dmitri Mendeleev (1834-1907) In 1869, Mendeleev developed the periodic classification of elements Arranged 63 known elements in order of atomic mass Placed elements with similar physical and chemical properties in the same group Left gaps in the table for elements yet to be discovered

Overview (so far)

Metals Found on the left side of the staircase (under the stairs) Physical properties Solid at room temperature (except mercury) Lustre (shine) Conducts heat/electricity Malleable (bendable) ductile (stretched into wires) as solid High melting and boiling points

Non-Metals Found on the right side of the staircase (to the right of the staircase) Physical Properties Solid, liquid or gas at room temperature NOT lustreous Brittle, hard, or soft POOR conductors The opposite to the metals!

Metalloids Found touching the stairs Have BOTH metallic and non metallic properties Physical properties tend to be that of metals Chemical properties tend to be that of non-metals Used in computer industry

Metalloids Groups 3-12 Generally stable metals Not as easily predictable Many form ions with more than one possible charge Most common indicated on periodic table by the top number

Trends Elements arranged according to their properties and atomic mass All elements in the same period have the same ENERGY LEVELS Elements of the same group have the same number of VALENCE ELECTRONS

Groups to know! Group 1 – Group 2 – Group 17 – Group 18 –

Alkali Metals Very reactive Donate one electron Very soft, do not occur freely in nature Why do you think that is?

Alkaline Earth Metals Berylium Magnesium Calcium Strontium Barium

Halogens Fluorine Chlorine Bromine Iodine Astatine

Noble Gases Helium Neon Argon Krypton Xenon Radon