PartChargeLocation ProtonPositive (+)In the nucleus NeutronNeutral ( )In the nucleus ElectronsNegative (-)Orbiting around the nucleus

 He created the periodic table of elements in At this time there were 63 elements.  He noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass.  The table we read today is arranged according to increasing atomic number.

Each square on the periodic table includes:  Atomic number  Chemical Symbol  Chemical Name  Atomic mass

 Mass number - sum of the protons and neutrons in the nucleus.  Atomic mass - the average mass of all isotopes of an element.  Atomic number - the number of protons in the nucleus.  Isotopes - atoms with the same number of protons and a different number of neutrons. Example: Carbon 12, 13, and 14.

Periods  Horizontal Rows (Numbered 1 – 7) Groups  Vertical Columns (Numbered 1 – 18)

 Luster - shininess  Malleable-hammered, pressed, or bent into shape  Ductile-pulled or drawn out into wire  Conductive-ability to transfer heat or electricity  Color-produced when heated  Magnetic-attracted to a magnet or become magnetic

 Reactivity-ease and speed with which an element combines, or reacts with other elements and compounds  Corrosion-the destruction of a metal as it is exposed to other elements or compounds

 Group 1 (Alkali Metals) – most reactive group of metals, shiny and soft  Group 2 (Alkaline Earth Metals) – reactive, fairly hard and good conductors of electricity  Groups 3 – 12 (Transition Metals) – hard, shiny, good conductors of electricity  Group 17 – (Halogens) – highly reactive nonmetals, salt-forming  Group 18 – (Noble Gases) – nonreactive, very stable

 Dull  Brittle (break apart easily)  Poor conductors of heat and electricity  Most are gases  Gain electrons easily

 These elements share some characteristics of the metals and those of the nonmetals.  The most useful property of the metalloids is their varying ability to conduct electricity.  Semiconductors - substances that can conduct electricity under some conditions but not under other conditions