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?