Download - Atoms and the periodic table
Atoms on the Periodic Atoms on the Periodic TableTable
December 17, 2012December 17, 2012
ObjectivesObjectives
1.1. Describe the present model of the Describe the present model of the atom explaining electrons, neutrons, atom explaining electrons, neutrons, and protonsand protons
Periodic TablePeriodic Table
Atoms make up all matterAtoms make up all matter
Elements are any material that is made up Elements are any material that is made up of only one type of atomof only one type of atom
Elements are organized onto the periodic Elements are organized onto the periodic tabletable
Each element is designated an atomic Each element is designated an atomic symbol on the periodic tablesymbol on the periodic table
AtomsAtoms
Atoms cannot be Atoms cannot be seen with visible lightseen with visible light
Robert Brown Robert Brown
First to discover direct First to discover direct evidence of the atomevidence of the atom
An Atom is made up of three parts:An Atom is made up of three parts: ProtonsProtons NeutronsNeutrons ElectronsElectrons
ElectronsElectrons
Electrons surround the nucleus in an Electrons surround the nucleus in an electron cloudelectron cloud
Electrons carry a negative chargeElectrons carry a negative charge
The atom is mostly empty spaceThe atom is mostly empty space
Electron Cloud ModelElectron Cloud Model
Why don’t we pass through one another?Why don’t we pass through one another?
Electrical repulsion – two electrons with Electrical repulsion – two electrons with negative charges will repel each othernegative charges will repel each other
ProtonsProtons
Protons and neutrons are bound to the Protons and neutrons are bound to the atomic nucleusatomic nucleus
Protons carry a positive chargeProtons carry a positive charge
Protons are identified by Protons are identified by Atomic numberAtomic number
atom is electrically neutral: Number of atom is electrically neutral: Number of protons = number of electrons; protons = number of electrons;
NeutronsNeutrons
Neutron has no electrical charge, but the Neutron has no electrical charge, but the same mass as a protonsame mass as a proton
Protons and neutrons are called nucleonsProtons and neutrons are called nucleons
Mass given to each proton and neutron is 1Mass given to each proton and neutron is 1
Atomic MassAtomic Mass
• Electrons are so small they are considered Electrons are so small they are considered negligible in massnegligible in mass
• Atomic mass is measured in the unit – Atomic mass is measured in the unit – amuamu Atomic Mass UnitAtomic Mass Unit
Atomic mass on the periodic tableAtomic mass on the periodic table
Mass Number, Isotopes and Ions
December 18, 2012
Electrons are so small they are considered Electrons are so small they are considered negligible in massnegligible in mass
Protons and neutrons in the nucleusProtons and neutrons in the nucleus
• Atomic mass is measured in the unit – Atomic mass is measured in the unit – amuamu Atomic Mass UnitAtomic Mass Unit
Atomic MassAtomic Mass
Atomic mass on the periodic table – Atomic mass on the periodic table – averageaverage of all its isotopes of all its isotopes
Isotope – an Element with differing Isotope – an Element with differing number of neutronsnumber of neutrons
Mass NumberMass Number
Mass number = total number of protons Mass number = total number of protons and neutronsand neutrons
Identify isotopes by the mass numberIdentify isotopes by the mass number
Agenda Bell work• Finish notes
• Practice Isotopes and Ions
• History of the Atom
• Atoms Quiz tomorrow
• Finish yesterday’s WS
• Distinguish between the following:– Atomic Number– Mass Number– Atomic Mass
• Define an Isotope• What identifies what an
element is?
Writing Isotopic SymbolsWriting Isotopic Symbols
X = element symbolX = element symbolA = Mass NumberA = Mass NumberZ = Atomic NumberZ = Atomic Number
Total number of neutrons:Total number of neutrons: Mass Number – Atomic number = number of Mass Number – Atomic number = number of
neutronsneutrons
Isotopic NotationIsotopic Notation
Hydrogen - 2, has one proton and one Hydrogen - 2, has one proton and one neutronneutron
Hydrogen - 3, has one proton and two Hydrogen - 3, has one proton and two neutronsneutrons
Ions
Atoms that gain or lose electrons
Lose electrons – positive in charge
Gain electrons – negative in charge
Hydrogen that has lost an electron
H+1
Hydrogen that has gained an electron
H-1