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