Periodic table

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 identified 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• Solid at room temp (exception: mercury

and hydrogen – nonmetal)• 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• 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- determines the number of energy levels

• Properties gradually change moving left to right across each row from reactive (group 1) to non-reactive (group 18)

• Columns 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 outer shell

• Group number determine the valence electrons (ex: group one – all elements in group 1 have 1 valence electron)

Energy Levels

• 1st energy level – 2 valence electrons (max)

• 2nd energy level – 8 valence electrons (max)

• 3rd energy level – 8 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.

Bonds

• To form bonds, elements must reach a full state of 8 valence electrons in the outermost energy level (octet rule) (Exception: would be first energy level which is full at 2-helium)

Group 1: Alkali metals

• Metals

• 1 valence electron in outer level (easily shared and form compounds easily)

• Very reactive with H2O, O2 and other elements

• Don’t appear in nature by themselves, only as compounds

Group 2 – Alkaline-Earth Metals

• Metals

• 2 valence electrons in outer level (slightly less reactive)

Group 3 – 12: Transition

• Metals

• 1 or 2 valence electrons in outer level (depending on element) and are less reactive

Lanthanides and Actinides

• 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

• 3 valence electrons in outer level and are semi reactive

Group 14-Carbon group

• 1 nonmetal, 2 metalloids and 2 metal

• 4 valence electrons in outer level and most non-reactive depending on element

• Forms organic compounds (all living things contain carbon)

Group 15-Nitrogen Group

• 2 nonmetals, 2 metalloids, 1 metal

• 5 valence electrons in outer level and reactivity depends on conditions and element

• P is extremely reactive and only appears in compounds

Group 16-Oxygen Group

• 3 nonmetals, 1 metalloid, and 1 metal

• 6 valence electrons in outer level and reactivity depends on element– Po-84 is radioactive

Group 17-Halogens

• Nonmetals

• 7 valence electrons in outer level and has violent reactions with alkali-metals to form salt compounds– Highly reactive with other elements– Do not appear in nature alone only in

compounds

Group 18-Noble Gases

• Nonmetals

• 8 valence electrons in outer level (full level) (except helium which has 2 valence electrons, which makes helium full) and very un-reactive – inert

• Do not form compounds under normal conditions

Hydrogen

• Nonmetal

• 1 electron in outer level so it is set above the alkali metals and is reactive

• Properties: even though above metal category, has properties of nonmetals

• Most abundant element in universe, makes up stars

• Atomic number = Number of Protons

• Electrons equal to the number of protons

• Neutrons equal atomic mass minus the protons

• Protons do not change in a atom, neutrons can change, electrons can be shared or transferred (when bonds are made)