what is the periodic table? compact way of organizing elements contains a lot of information allows...
TRANSCRIPT
What is the periodic table?
• compact way of organizing elements• contains a lot of information • allows us to make predictions about
behavior and properties of elements based on their positions in PT
• Element Song
History of the Periodic Table
• end of 1700’s – less than 30 elements known
• many elements discovered during 1800’s
• many experiments done to determine atomic masses of the new elements
John Newlands
• 1864: if arrange elements by atomic mass – properties: repeat every 8th element
• Law of Octaves – did not work for all known elements
• Key Idea was correct: properties of elements do repeat in periodic manner
Mendeleev & Meyer1869: Mendeleev produced 1st accepted PT
– elements: in columns according to ↑ atomic mass – elements with similar properties grouped together
•predictedpredicted existence & properties of undiscovered elements
• not totally correct –more accurate atomic mass calculations showed some elements were not in right place
Remember
1860’s:
• Dalton’s billiard ball model of the atom
• NO subatomic particles yet discovered
1913 – Henry Moseley
• by 1913, protons & electrons discovered– neutrons were predicted
• Moseley determined atoms of each element contain unique # protons (= atomic number)
• re-arranged Mendeleev’s PT according to atomic number instead of atomic mass
• problems with elements in wrong place disappeared
Periodic Law
There is a periodic repetition of the elements chemical and physical properties if they are arranged by increasing atomic numberincreasing atomic number
Glenn Seaborg: 1950’s
• Lanthanide and Actinide Series
Seaborg
Mendeleev
Mosley
Newlands
Classifying the Elements
• 2/3 (75%) of elements are metalsmetals• remaining elements: non-metalsnon-metals &
metalloidsmetalloids (semi-metals)• metalloids:
– have properties of both metals & non-metals
• staircasestaircase:: – dividing line between metals & non-metals – elements to left are metals (except H)– elements to right are non-metals
Vocabulary of PT• columns called groupsgroups or familiesfamilies
– today: #1 thru 18, Arabic numerals– past: A & B groups, Roman numerals
• A-Group (tall columns)– columns 1,2,13-18 (= representative elements)– IA – 8A
• B-Group (short columns)– transition metals (columns 3-12)– IB - 8B
• rows are called seriesseries or periodsperiods– #1 thru 7
Column numbering (1 18) left to right
Period numbering (1 7) top to bottom
Names of FamiliesAKA: A group elements
Group 1 = Alkali Metals
Group 2 = Alkaline Earth Metals
Group 13 = Boron family
Group 14 = Carbon family
Group 15 = Nitrogen family
Group 16 = Oxygen family
Group 17 = Halogens
Group 18 = Noble Gases
AKA B group elements
Groups 3-12: Transition metals
Transition Metals
• Groups 3 through 12
• AKA group B elements
• Actinide & Lanthanide series – inner transition elements
• put the COLOR in your life– form brightly colored salts/solutions
Elements that are gases at STP
Diatomics:
H2, N2, O2, F2, Cl2
Monatomics: noble gases He, Ne, Ar, Kr, Xe, Rn
Two elements are liquid at room temperature
Br2 (non-metal) and Hg (metal)
All other elements are solids at room temperature
Structure of Periodic Table
• closely related to electron configuration of each element
Energy Levels = Row Number
• elements in same row have same # of principal energy levels – so # of principal energy levels = to row #
Going Across Row 2:Going Across Row 2:
2-8Ne18 (VIIIA)
2-7F17 (VIIA)
2-6O16 (VIA)
2-5N15 (VA)
2-4C14 (IVA)
2-3B13 (IIIA)
2-2Be2 (IIA)
2-1Li1 (IA)
ConfigurationElementFamily
Valence Electrons
• chemical behavior determined by # valence electrons
• elements with same # valence electrons will have similar chemical properties– elements in same column have similar
chemical properties
Going Down Column 1:Going Down Column 1:
2-8-18-32-18-8-1Fr7
2-8-18-18-8-1Cs6
2-8-18-8-1Rb5
2-8-8-1K4
2-8-1Na3
2-1Li2
1H1
ConfigurationElementPeriod
Valence Electrons
414 or IVA
313 or IIIA
22 or IIA
11 or IA
Number of Valence Electrons
Group
PROPERTIES of the
Elements
Properties of Metals
• malleable – flattened into sheets
• ductile – drawn into wires & tubes
• have Luster
• good conductors of heat & electricity
• solid at room temperature (except Hg)
• metals lose electrons & form positive ions ““Metals are losersMetals are losers””
• low ionization energy
• low electronegativity
Properties of Non-metals• generally gases or solids (except Br2)• solids are brittle• solids are dull• poor conductors of heat & electricity• non-metals gain electrons & form negative ions ““Non-metals are winnersNon-metals are winners””• high ionization energy• high electronegativity
Properties of Metalloids7 metalloids:
– 5 on right of staircase: B,Si,As,Te,At– 2 on left of staircase: Ge,Sb
Each metalloid has some metallic and some non-metallic properties
example: Sishiny like metal but
brittle like non-metal