Intro to Chemistry

Atomic Structure  Nucleus- center of an atom -contains protons (which are positive) -contains neutrons (which are neutral) Ex- Sodium:

Bohr Model of Atom

Atomic Structure Outside the Nucleus:  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 = SAVE 4 th energy level = FOR CHEMISTRY!!

Subatomic Particles Organized ChargeLocationMass Protons Neutrons Electrons

Subatomic Particle Organized ChargeLocationMass ProtonsPositiveIn nucleus1 amu NeutronsNeutralIn nucleus1 amu ElectronsNegative Outside of nucleus/ in energy levels 0 amu Atomic Mass

An atom is defined by the number of PROTONS IT HAS!!!

Chemistry tidbits  Chemical Symbol- letter representing the atom (sometimes from Latin)

Chemistry tidbits  Atomic number = number of protons  Mass number = # protons + # neutrons  Don’t bother to weigh the air inside the box  So how can you calculate NEUTRONS??

Calculating Neutrons is a simple algebraic problem…  Mass Number = protons + neutrons  Atomic Number = protons  Write the equation…  Mass Number= Atomic Number + neutrons  #Neutrons = (mass number – atomic number)

Chemistry tidbits  Usually can assume:  # protons = # electrons  ONLY true for NEUTRAL ATOMS!

And remember…  Don’t mess with the  PROTONS!!!

So what CAN we “mess with?”  Neutrons…  Changes the MASS  Get an ISOTOPE  Electrons…  Changes the CHARGE  Get an ION

Atomic Mass Mystery…  Look at the atomic mass for Oxygen. What does it say (exactly?)   What is the atomic mass?  P + N  So what the heck!?!?!  Average of the actual isotopes on Earth!!!

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

How to write isotopes…  Mass/Hyphen Notation:  Especially important for a form of the isotope that is NOT the “usual”  Write the symbol, a dash, and the mass # for that isotope  Ex’s  C-14  C-12

How to write isotopes…  Nuclear Symbol Notation  Includes the symbol, atomic #, and the mass # for that isotope  Ex’s 14 6 C

What else CAN we “mess with?”  Neutrons…  Get an ISOTOPE  Electrons…  Get an ION

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)

Intro to Periodic Table

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)  ONE EXCEPTION  Hydrogen!  vertical columns (#1-18)  Groups  horizontal rows (#1-7)  Periods

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 Metals  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  You’ll learn more in chemistry about these elements

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 Periodic table

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 