Chapter 5 Periodic Table

Mendeleev Chemist that looked for patterns among their properties of elements Used pieces of paper and wrote the names and properties of the elements Arranged items due to increasing atomic mass Periodic – have regular, repeating pattern

When he arranged the elements according to atomic mass, similar chemical and physical properties were observed every 8 th element Left spaces for missing elements Used his table because when missing elements were found they fit in locations where Mendeleev thought they would

Changing the Arrangement Some locations for elements was incorrect until Henry Moseley figured it out He determined the number of protons (atomic number) for each element and put them in order according to atomic number Periodic Law

Each element is identified by its chemical symbol Each square on periodic table has its symbol, atomic number, atomic mass and name Each symbol contains one or two letters First letter is always capital and if there is a second letter it is lower case

Rows = periods (left to right) –Repeating patterns Columns = groups (up and down) –Similar physical and chemical properties –Sometimes called a family

Metals Good conductors of heat Malleable Shiny Ductile Most elements are metals Left side of periodic table Most are solid at room temp (except mercury)

Nonmetals Not shiny Not malleable Not ductile Poor conductors of heat Found on right side of periodic table More than half are gases at room temp

Metalloids Called semiconductors Some properties of metals and nonmetals Can be shiny, brittle, hard, soft, etc

Grouping Elements Group 1 –Most reactive metals –Called alkali metals –Very soft metals –Shiny –1 valence electron (electron in outer shell)

Group 2 –Very reactive metals (less than alkali) –2 valence electrons –Called Alkaline Earth Metals

Groups 3-12 –Called transition metals –1 or 2 valence electrons –Less reactive –Shiny –Good conductors of heat –Found between metals and nonmetals

Lanthanides –Follow transition metal lanthanum –Shiny reactive metals Actinides –Follow transition metal actinium –Radioactive (unstable)

Group 13 –Boron Group One metalloid and four metals Reactive Solid at room temp 3 valence electrons

Group 14 –Carbon Group One nonmetal, 2 metalloids, and 2 metals 4 valence electrons Solid at room temp Reactivity varies

Group 15 –Nitrogen Group 2 nonmetals, 2 metalloids, and 1 metal 5 valence electrons Reactivity varies All but nitrogen are solid at room temp Nitrogen = 80% of air you breathe

Group 16 –Oxygen Group 3 nonmetals, 1 metalloid and 1 metal 6 valence electrons Reactive All but oxygen are solid at room temp Oxygen makes up 20% of air

Group 17 –Halogens Nonmetals 7 valence electrons Very reactive Poor conductors of heat Never alone in nature React violently with alkali metals

Group 18 –Noble Gases Nonmetals Nonreactive 8 valence electrons except for He Colorless Odorless Gases at room temp Found in Earth’s atmosphere

Hydrogen –1 valence electron –Reactive –Colorless –Odorless –Gas at room temp –Low density –Reacts with oxygen –Stands apart from other elements