The Periodic Table

Atomic Structure Nucleus- center of an atom -contains protons - which are positive -contains neutrons- which are neutral Electrons (which are negative) surround the nucleus in energy levels 1 st energy level = holds 2e 2 nd energy level = holds 8e 3 rd energy level = holds 18e 4 th energy level = holds 32e

Bohr Model of Atom

More Chemistry tidbits Atomic number = number of protons Mass number = # protons + # neutrons #Neutrons = mass number - # protons # protons = # electrons

Isotopes Isotopes are different atoms of the same element that contain the same number of protons but different number of neutrons. Examples Cl-35 vs. Cl-37 17P 17P 18N 20N

Periodic Table tidbits Period table organization – organized by increasing atomic number Split into metals (left side of stair step line) and nonmetals (right side of stair step line) Metalloids- surround the stairstep line Groups (families) – vertical columns (#1- 18) Periods – horizontal rows (#1-7)

Metals-left side of table Exist as solids at room temperature Shiny Good conductors of heat & electricity Malleable (can be bent)

Nonmetals-right side of table Most are gases at room temperature Some are brittle solids- carbon, sulfur, iodine, & phosphorus Most do not conduct heat & electricity well

Metalloids- next to zigzag line b/w metals & nonmetals Properties fall between neighbors on both sides Most are silvery in appearance, brittle, poor conductors of heat & electricty

Transition elements Metals- which are less reactive than the alkali or alkaline earth metals Often exist as oxide or sulfide ores ex. Iron sulfide or iron oxide

Major Groups on periodic table Alkali metals- group 1- most reactive Alkaline earth metals- group 2 Transition metals- groups 3-12 Metalloids- surround stairstep line Halogens- group 17 Noble gases-group 18 (inert gases-stable; nonreactive) Periodic table

Chemical Bonding Octet Rule- Atoms bond with one another in order to become stable (need to get 8 electrons in outer ring) Exception- hydrogen only needs 2 electrons in outer ring to be stable Bonds are forces of attraction between elements Involves bonding of valence electrons (electrons in outermost shell)

Lewis Dot Structures Lewis dot diagrams- display the number of valence electrons (outermost electrons) around the element symbol Used to show how atoms of different elements bond and form compounds Hint- use group number to find valence electrons

Electron configurations

Lewis Dot Diagrams