Post on 14-Feb-2017
Periodic Table
• Dmitri Mendeleev-recognized that elements had repeating patterns (periodic) and organized elements into a table by increasing atomic mass
• With table he was able to predict that there would be elements still unidentified by the gaps in his table
• Henry Moseley - determined that the number of protons - atomic number (which is unique to each element) would allow the elements to fit into very specific pattern
• All elements follow the Periodic Law – chemical and physical properties change periodically with atomic number
Metals
• Most elements are metals• Found to the left of the zigzag line
(exception: hydrogen)• Solid at room temp (exception: mercury)
Properties:– Shiny– Ductile– Malleable– Good conductors
Metalloids
• Also called semiconductors• Border the zigzag line (exception Al)• Have properties of both metals and
nonmetals depending on the conditions• properties: depending on conditions
– Brittle– Good conductors– Some shiny (others dull)
nonmetals
• More than half are gases at room temp• To the right of the zigzag line• Properties:
– Not malleable or ductile– Not shiny or dull– Poor conductors
Each square on table
• Each square includes:• elements name• chemical symbol (color coded to identify
if element is a solid, liquid or gas at room temp)
• Atomic number (protons)• Atomic mass (weighed average of isotopes)• Background color (identifies metals,
nonmetals and metalloids on table)
• First letter of chemical symbol is always upper case and any additional letters are lower case
• Newest elements have temporary 3 letter symbols• Rows (left to right) are called periods • Rows-determines the number of energy levels
– 7 rows on the table• Properties gradually change moving left to right
across each row from reactive (group 1) to non-reactive (group 18)
Energy Levels• 1st energy level – 2 valence electrons (max)• 2nd energy level – 8 valence electrons (max)• 3rd energy level – 18 valence electrons (max)• And so on….• Each energy level can have less valence
electrons but they can not have more than the maximum valence electrons.
• Columns (up and down) are called groups or family• Elements in the same group or family have similar
properties moving up and down each column• Each element in a family has the same number of
valence electrons in the last energy level• Group number determine the valence electrons (ex:
group one – all elements in group 1 have 1 valence electron, all of the elements in group 2 have 2 valence and so on)
Bonds
• To form bonds, elements must reach a full state of 8 valence electrons in the last energy level (octet rule)
• (Exception: Helium - would be first energy level which is full at 2)
Group 1: Alkali metals
• Metals• Valence 1 • Very reactive with H2O, O2 and other
elements• Makes compounds with halogens (group
17) easily to form salts
Group 2 – Alkaline-Earth Metals
• Metals• Valence 2
Group 3 – 12: Transition
• Metals• Valence 1 or 2 (depending on element)
Lanthanides and Actinides(Rare earth metals)
• In periods 6 and 7 and appear at the bottom of the periodic table to keep table from being to wide
• Lanthanides are shiny reactive metals• Actinides are unstable radioactive• All elements after Pu-94 (plutonium) are
man-made in labs and don’t occur in nature
Group 13: Boron Group
• Has 1 metalloid and 4 metals• Valence 3
Group 14-Carbon group
• 1 nonmetal, 2 metalloids and 2 metal• Valence 4 • Carbon forms organic compounds (all
living things contain carbon), makes more compounds than any other element
Group 15-Nitrogen Group
• 2 nonmetals, 2 metalloids, 1 metal• Valence 5 • P is extremely reactive and only appears
in compounds
Group 16-Oxygen Group
• 3 nonmetals, 1 metalloid, and 1 metal• Valence 6
Group 17-Halogens
• Nonmetals• Valence 7 • has violent reactions with alkali-metals
(group 1) to form salt compounds– Highly reactive with other elements– Do not appear in nature alone only in
compounds
Group 18-Noble Gases
• Nonmetals• Valence 8 valence (full level) • except helium which has 2 valence
electrons, which makes helium full • very un-reactive – inert • Do not form compounds
Hydrogen
• Nonmetal• Valence 1 electron in last energy level so it
is set above the alkali metals• Properties: even though above metal
category, has properties of nonmetals• Most abundant element in universe,
makes up stars
• Protons = Atomic number • Electrons = protons• Neutrons = mass number (rounded)
minus the protons• Protons do not change in a atom, • neutrons can change (isotopes), • electrons can be shared or transferred
(when bonds are made)
Reflection Questions • 1. What are the seven horizontal rows of the
table called? How are the elements of a row related?
• 2. What are the vertical columns of the table called? How are the elements of each column related?
3.What basic information is contained in the table?