CHAPTER 3 INTRODUCTION TO THE PERIODIC TABLE

The Periodic Table Based on repeating patterns Patterns help us predict things Ex: Calender months Breakfast, lunch, dinner Seasons Days: sunset, sunrise, moon rise Phases of moon Tides Chemists place elements into groups based on similar properties Helps predict characteristics of elements easily.

Periodicity: pattern of repeating order How does a systematic arrangement of things make it easier to use? Examples Periodic Law: physical and chemical properties of the elements tend to repeat in a systematic manner with increasing atomic number

HISTORY OF PERIODIC TABLE 1860’s – 60 elements aleady discovered - Scientists grouped similar elements in a table ex: Cu, Ag, Au: coinage metals Li, Na, K: alkalai metals Cl, Br, I: halogens - Also wanted to show differences in a table

1829 – Dobereiners Triads (German) - classified elements into groups of 3 (triads) - triad had similar chem. and phys. properties - middle element lies ½ way between other elements - useful because element had similar chemical and physical properties

1871 – Dimitri Meldeleev (Russian) - responsible for first periodic table - realized chem and phys properties of elements repeated in orderly way when organized by atomic mass - listed elements by atomic mass - table resembles modern periodic table - contained 63 elements

Modern Periodic Table - systematic listing of elements in a table - organized by atomic number (number of protons) known elements (natural and synthetic)

INFORMATION FOUND ON PERIODIC TABLE atomic numbers (# protons) number of electrons number of valence electrons atomic symbol state of element number of neutrons

ARRANGEMENT OF PERIODIC TABLE Periods - horizontal rows - numbered 1-7 on left side of table Families/Groups - vertical columns - labeled with either Roman numerals and letters (old) or numbers 1-18 (newer) Metals, Metalloids, Non metals - three types of elements - color coded

CHARACTERISTICS OF FAMILIES AND PERIODS Periods - horizontal rows - atomic number increases by 1 as moves to right - chemical properties not all that similar Families - vertical columns - labeled with roman numeral and letter or numbers - similar chemical properties - same number of valence electrons in all members of family – react same way in reactions

Important Families Alkali Metals - Group 1 -lose 1 electron in chem rxns. -most reactive of all of the metals -combine with non-metals to form salts

Important Families Alkaline Earth Metals - Group 2 - lose 2 electrons -become more soluble as temperature decreases -ex: Ca: important for bones beryllium magnesium calcium strontium barium radium

Important Families Halogens - Group 17 (non-metals) - gain 1 electron -when combined with metals they are salt like -exist as gases, liquid, and solids -very toxic to cells ex: Cl and I (both disenfectants) flourine chlorine bromine iodine astatine

Important Families Noble Gases -Group valence electrons (full valence shell) -He: has 2 valence electrons (full valence shell) - very non reactive and stable Ex: helium used in blimps neon lights arc welding helium neon argon krypton xenon radon

Important Families Transition -Groups 3 – 12 -act as catalysts in reactions and are often colorful in compounds -make the strongest magnets -Have varying numbers of valence electrons Inner Transition Metals (Rare Earth) Lanthanides (58-71) - rare earth elements - <1% of earth - have similar properties Actinides (90-103) - all radioactive - all synthetic except uranium

TYPES OF ELEMENTS Metals - solids (exceptions –Mercury Hg, and Bromine Br) - shiny - good conductors of electrity and heat - ductile – can be drawn into a thin wire - malleable – easily hammered into thin sheets - lose 1,2,3 electrons in chem. rxns. - most elements on table are metals (occupy left and center) - very high melting point

TYPES OF ELEMENTS Non Metals - brittle (break easily) - not malleable or ductile - poor conductors of electricity and heat - hold valence electrons tightly and tend to gain or share electrons in chem reactions - some non metals are liquid - gases located in upper right corner except H

TYPES OF ELEMENTS Metalloids - semi metals that have properties between - metals and non metals (stair step) - partially conduct electricity - don’t conduct electricity as well as metal, but better than non-metals *economically important because used in semiconductors in computer chip industry Silicon (2nd most abundant element in Earth after carbon)

Use of the Periodic Table Find the element using the information below PeriodGroupElement

WITH YOUR KNOWLEDGE OF THE PERIODIC TABLE AND PROPERTIES OF ELEMENTS, YOU WILL BE ABLE TO PREDICT HOW ELEMENTS FORM COMPOUNDS AND WHICH COMPOUNDS THEY FORM

Study for the test !