chapter 2 notes atomic structure. atoms democritus – ancient greek science dude, 1 st proposed the...
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Chapter 2 NotesChapter 2 Notes
Atomic StructureAtomic Structure
AtomsAtoms
Democritus – Ancient Greek Science Democritus – Ancient Greek Science dude, 1dude, 1stst proposed the idea of atoms, tiny proposed the idea of atoms, tiny indivisible particlesindivisible particles
Atomos – ancient Greek word for Atomos – ancient Greek word for indivisibleindivisible
John Dalton’s Atomic TheoryJohn Dalton’s Atomic Theory
1.1. All elements are composed of All elements are composed of submicroscopic particles called atomssubmicroscopic particles called atoms
2.2. Atoms of the same element are identical. Atoms of the same element are identical. Atoms of one element are different from Atoms of one element are different from atoms of another elementatoms of another element
3.3. Atoms of different elements can combine Atoms of different elements can combine in simple whole number ratios to form in simple whole number ratios to form compoundscompounds
Cont.Cont.
4. Chemical rxn’s occur when atoms are 4. Chemical rxn’s occur when atoms are separated, joined or rearranged. However, separated, joined or rearranged. However, atoms of one element are never changed atoms of one element are never changed into atoms of another element as the result into atoms of another element as the result of a chemical reaction.of a chemical reaction.
ATOMATOM- the smallest particle of an element - the smallest particle of an element that retains the properties of that elementthat retains the properties of that element
Electrons, Protons and NeutronsElectrons, Protons and Neutrons
ElectronsElectrons- are negatively charged particles- are negatively charged particles
– Discovered by Discovered by J.J. ThomsonJ.J. Thomson in 1897 by in 1897 by bending a charged beambending a charged beam
– Elektron (greek) shining beamElektron (greek) shining beam
– http://www.chem.uiuc.edu/clcwebsite/video/Cath.mov
ProtonsProtons
Positively charged particlePositively charged particle
Discovered 1886 – E. GoldsteinDiscovered 1886 – E. Goldstein
Discovered by Henry Mosley in 1911Discovered by Henry Mosley in 1911
Protos (greek) firstProtos (greek) first
NeutronNeutron
Subatomic particle with no chargeSubatomic particle with no charge
Discovered by Discovered by James ChadwickJames Chadwick in 1932 in 1932
SymbolSymbol ChargeCharge Mass Mass (AMU)(AMU)
ElectronElectron ee-- -1-1 1/18401/1840
ProtonProton pp++ +1+1 11
NeutronNeutron nn00 00 11
The Structure of the Nuclear AtomThe Structure of the Nuclear Atom
Nucleus – central core of the atom, Nucleus – central core of the atom, composed of protons and neutronscomposed of protons and neutrons
Discovered by Earnest Rutherford in 1911Discovered by Earnest Rutherford in 1911
Gold foil Experiment
Atomic NumberAtomic Number
The number of protons in the nucleus of an The number of protons in the nucleus of an atomatom
Neutral atoms – have equal # pNeutral atoms – have equal # p++ (+ charge) (+ charge) and eand e-- (- charge) (- charge)
Mass NumberMass Number
Number of pNumber of p++ and n and n0 0 in the nucleusin the nucleus
pp+ + + n + n00 = mass = mass
Isotopes of ElementsIsotopes of Elements
Isotopes: Atoms that have the same Isotopes: Atoms that have the same number of protons, but different numbers number of protons, but different numbers of neutronsof neutrons
Carbon – 12Carbon – 12
Carbon – 13Carbon – 13
Carbon - 14Carbon - 14
Atomic MassAtomic Mass
Atomic Mass Unit (amu) – 1/12 the mass Atomic Mass Unit (amu) – 1/12 the mass of a Carbon – 12 atomof a Carbon – 12 atom
Atomic Mass – The weighted average Atomic Mass – The weighted average mass of the isotopes in a naturally mass of the isotopes in a naturally occurring sampleoccurring sample
Calculating Atomic MassCalculating Atomic Mass
Ex. Magnesium: Ex. Magnesium: Magnesium – 24 78.70%Magnesium – 24 78.70%
Magnesium – 25 10.13%Magnesium – 25 10.13%
Magnesium – 26 11.17%Magnesium – 26 11.17%
Multiply the mass number by the percent and Multiply the mass number by the percent and add up the answers to get the average mass.add up the answers to get the average mass.
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