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Atomic Models. Around 400 BC a Greek scientist called Democritus said that matter was made up of small particles he named 'Atoma' (meaning indivisible). Dalton - 1803 - round ball with a positive nucleus Element made up of atoms that cannot be divided Atoms of the same element are alike - PowerPoint PPT Presentation
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Atomic Models
Around 400 BC a Greek scientist called Democritus said that matter was made up of small particles he named 'Atoma' (meaning indivisible).
Dalton - 1803 - round ball with a positive nucleusElement made up of atoms that cannot be divided Atoms of the same element are alikeAtoms of different elements can join in whole number ratios to form molecules
Thompson - discovered electrons in 1897
Based on his alpha-particlescattering experiment on gold, Rutherford concludedthat the atom consisted ofa hard central core wheremost of the mass of theatom rested.
Rutherford - discovered the nucleus 1911
http://www.learnerstv.com/animation/animation.php?ani=121&cat=chemistry
Bohr - electrons travel in paths (energy levels) around the nucleus - 1913
http://web.visionlearning.com/custom/chemistry/animations/CHE1.3-an-atoms.shtml
Protons
PositiveMass = 1 amu = 1.67 x 10-24 gDiscovered by E. Goldstein in 1886Symbol – p+Electrons
Negative chargedMass = 1/1840 amu = 9.11 x10-28Discovered by J.J. Thompson in 1897 Symbol – e-1
Neutrons
NeutralMass = 1 amu = 1.67 x 10-24gDiscovered by James Chadwick in 1932Symbol - no
The Atomic Nucleus
Small DensePositive chargeCore of an atomContains protons and neutronsDiscovered by Ernest Rutherford in 1911
P+No
Valence electron - an electron in the outermost energy level of an atom
Chadwick - discovered the neutrons in 1932
Modern Theory - electrons do not move in definite paths but the exact position, speeds and direction of electrons cannot be determined.
Modern - electron cloud theory replaced Bohr’s model in 1925 http://
intro.chem.okstate.edu/1314F97/Chapter6/BohrQuantum.html
e- enter lowest energy level first
p orbitals can hold a maximum of two electrons so all three together can hold a total of 6 electrons
As s orbital is shaped lie a sphere, so it has only one possible orientation in space. An s orbital can hold a maximum of two valence electrons
http://micro.magnet.fsu.edu/electromag/java/atomicorbitals/index.html
The Atom
2 protons = +22 neutrons = 02 electrons = -2Net charge = 0
Atomic NumberAtoms are composed of protons, neutrons and electronsElectrons surround the nucleus and occupies most of the volume of the atomThe number of protons in the nucleus of an atomEach element has a different number of protons; therefore, a different atomic numberNumber of protons = number of electronsTherefore the atom is neutral
P+no
e-
e-
e-
e-
The Atom – mostly empty space
Mass Number
Most of the mass of an atom is in the nucleusProtons = 1 amuNeutrons = 1 amuElectron = 1/1840 amuMass Number = Protons + NeutronsNeutrons = Mass number - Protons
12
C 6
Mass Number
Symbol
Atomic Number = p+
Neutrons = Mass Number - Atomic Number
3.2.9
Isotopes
IsotopesSame number of protons and electronsDifferent number of neutronsTherefore – Different mass numbers
10p+11no
10p+10no
10p+12no
20
Ne10
22
Ne10
21
Ne10
Atomic Mass
Atomic mass = weighted average of the masses of its isotopesYou calculate the atomic mass based on relative abundanceExample: Copper atomic mass= 63.546Isotopes – Cu-63 and CU-65Isotope Cu-63 more abundant
Y-10 20%
Y-21 80%
mass X % = Relative Weight10 X .20 = 221 X .80 =16.8 Total = 18.8 amu
MASS Weigh Add
Number Count Add
Average Mass
Mass/ Number
Don't do
% Part/Whole X100
Should equal 100
Relative abundance
Divide % by 100
Should equal 1
Relative Weight
Relative Abundance X Average Mass
Add
Kidney Brown Mac Total
http://www.quia.com/cb/147081.html
Atomic Structure Jeopardy
http://www.quia.com/hm/110454.html
Hangman
http://www.quia.com/rr/70834.html