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 1st energy level = holds 2e 2nd energy level = holds 8e 3rd energy level = holds 18e 4th 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