chapter 3 introduction to the periodic table. the periodic table based on repeating patterns...
TRANSCRIPT
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
SeasonsDays: sunset, sunrise, moon risePhases of moonTides
• 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)
- 112 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
berylliummagnesium calcium strontium bariumradium
Important FamiliesHalogens
- 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)
flourinechlorinebromineiodineastatine
Important FamiliesNoble Gases
-Group 18
-8 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
heliumneonargonkryptonxenonradon
Important FamiliesTransition- 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 ELEMENTSNon 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 ELEMENTSMetalloids
- 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 TableFind the element using the information below
Period Group Element
1 18
3 13
7 5
2 15
5 11
4 17
6 1
3 17
1 1
5 4
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 !