Why don’t we pass through one another?Electrical repulsion – two electrons withnegative charges will repel each other
ProtonsProtons and neutrons are bound to theatomic nucleusProtons carry a positive chargeProtons are identified by Atomic numberatom is electrically neutral: Number ofprotons = number of electrons;
NeutronsNeutron has no electrical charge, but thesame mass as a protonProtons and neutrons are called nucleonsMass given to each proton and neutron is 1
Atomic Mass• Electrons are so small they are considered negligible in mass• Atomic mass is measured in the unit – amu Atomic Mass Unit Atomic mass on the periodic table
Mass Number, Isotopes and Ions December 18, 2012
Electrons are so small they are considered negligible in mass Protons and neutrons in the nucleus• Atomic mass is measured in the unit – amu Atomic Mass Unit
Atomic MassAtomic mass on the periodic table –average of all its isotopesIsotope – an Element with differingnumber of neutrons
Mass NumberMass number = total number of protonsand neutronsIdentify isotopes by the mass number
Agenda Bell work • Finish yesterday’s WS• Finish notes• Practice Isotopes and • Distinguish between the Ions following: – Atomic Number – Mass Number• History of the Atom – Atomic Mass• Atoms Quiz tomorrow • Define an Isotope • What identifies what an element is?
Writing Isotopic SymbolsX = element symbolA = Mass NumberZ = Atomic NumberTotal number of neutrons: Mass Number – Atomic number = number of neutrons
Isotopic NotationHydrogen - 2, has one proton and oneneutronHydrogen - 3, has one proton and twoneutrons
IonsAtoms that gain or lose electronsLose electrons – positive in chargeGain electrons – negative in charge
Hydrogen that has lost an electron H+1Hydrogen that has gained an electron H-1
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