2 4.2/4.3 The Structure of the Atom & Modern Atomic Theory JOURNAL:QUIETLY work on the Atomic Math worksheet FIRSTThen, work on the“Not So Bohr-ing Atoms” Worksheet from the back table.Use the Periodic Table I gave you to help you.
3 Studying Atoms ANCIENT GREEKS- DEMOCRITUS: “atomos” = indivisible, uncutDifferent types of atoms with specific propertiesARISTOTLE:Only 4 elementsNo limit to divisions
4 Studying AtomsDALTON’S ATOMIC THEORY: all matter is made of particles that cannot be dividedEvidence:Compounds have fixed compositionsH2OChemical reactions are a rearrangement of solid atoms.
5 Studying AtomsTHOMSON’S ATOMIC THEORY: all matter is made of particles that CAN be dividedEVIDENCE:Particles collected on metal plateThe particles ALWAYS had a mass 1/2000 of a Hydrogen atom.The beam was always attracted to the positive side
6 Thomson’s “plum pudding” Atomic Model Explained neutral atoms with charges
7 Thomson’s “plum pudding” Atomic Model Studying AtomsRUTHERFORD’S ATOMIC THEORY: all atoms positive charge is concentrated in the nucleusThomson’s “plum pudding” Atomic Model
8 Studying AtomsRUTHERFORD’S ATOMIC THEORY: all atoms positive charge is concentrated in the nucleusDiscovered:Uranium emits fast moving positive particles
9 SHOULD GO STRAIGHT THROUGH!! Studying AtomsRUTHERFORD’S ATOMIC THEORY: all atoms positive charge is concentrated in the nucleusIf you shoot these positive particles at other atoms (Thomson’s plum pudding atom), what would happen to the particle?SHOULD GO STRAIGHT THROUGH!!
11 4.1 The Gold Foil Experiment RUTHERFORD’S ATOMIC THEORY: all atoms positive charge is concentrated in the nucleus
12 Studying Atoms – Modern Atomic Theory Bohr Atom:Electrons are in energy levelsElectrons move when they gain or lose energy(example)
13 Subatomic particles – distinguished by mass, charge and location Parts of an ATOM:Subatomic particles – distinguished by mass, charge and location
14 Subatomic particle PROPERTIES Protons (p+): In the nucleusCharge of 1+Mass of 1DEFINES THE ELEMENT(equals the ATOMIC NUMBER)
15 Protons (p+):Atoms of DIFFERENT elements have DIFFERENT numbers of protons
16 Subatomic particle PROPERTIES Neutrons (n°): In the nucleusNO chargeMass of 1Protons + neutrons = the ATOMIC MASS
17 ISOTOPES Neutrons (n°): Atoms of the same element with DIFFERENT numbers of neutrons are calledISOTOPES
18 Neutrons (n°):ISOTOPES of Hydrogen. Same Atomic #, different Mass #
19 Electrons (e-): In ENERGY LEVELS around the nucleus Charge of 1- Mass of 1/1836 of a p+Equal to the number of protonsThe outermost shell of electrons is called the VALENCE SHELL which holds the VALENCE ELECTRONS.Take out Bohr Diagram Sheet.
20 The most stable electron arrangement Electrons (e-):Change ENERGY LEVELS when the atom GAINS or LOSES energyThe most stable electron arrangement
21 Electrons (e-): CurrentTheory – “Electron Cloud Model” (p116-17) Orbitals that show most PROBABLE location of electrons
22 Electrons (e-):Atoms of the same element with different number of ELECTRONS are called IONS
24 4.2/4.3 The Structure of the Atom & Modern Atomic Theory OCTET RULE:Take out a lined sheet of paper, draw a circle for a nucleus and then three rings around the nucleus.2 electrons in 1st shellProtons and neutrons in nucleus8 electrons in 2nd shell8 electrons in 3rd shell
25 Atomic Number Practice Use your periodic table to find the atomic number of the following elements:Aluminum (Al)Titanium (Ti)Tin (Sn)Osmium (Os)Erbium (Er)How many protons does each atom have?The number of protons are equal to the atomic number.Al = 13Ti = 22Sn = 50Os = 76Er = 68
26 Mass NumberThe mass number of an atom is the sum of the number of protons and neutrons in the nucleus.ElementProtonsNeutronsMass NumberBoron565+6Carbon6+6Oxygen88+8Sodium111211+12Copper293429+341112162363
27 PracticeDetermine the number of protons and neutrons in the following atoms:Lithium – Atomic Number = 3Mass Number = 7Argon – Atomic Number = 18Mass Number = 39Strontium – Atomic Number = 38Mass Number = 88
28 Atomic Number & Mass Number If you know the atomic number and mass number, you can determine the number of neutrons. Mass Number - Atomic Number Number of Neutrons
29 AnswersDetermine the number of protons and neutrons in the following atoms:Lithium – Protons = 3Neutrons = 7 – 3 = 4Argon – Protons = 18Neutrons = 39 – 18 = 21Strontium – Protons = 38Neutrons = 88 – 38 = 50
30 Neutral Atoms In the nucleus, which particles have charge? ProtonsWhat charge do they have?PositiveWhat particle is opposite that charge?Electrons
31 (+3) + (-3) = 0, so the atom is neutral. Neutral AtomsIn the atom:The number of protons equals the number of electrons.Li has 3 protons, so has a charge of +3.Li also has 3 electrons that add up to -3.ADDED TOGTHER, the overall charge is:(+3) + (-3) = 0, so the atom is neutral.
32 Practice Magnesium, Protons = 12 Beryllium, Protons = 4 Determine how many electrons the following atoms have:Magnesium, Protons = 12Beryllium, Protons = 4Nitrogen, Atomic Number = 7Bromine, Atomic Number = 3512 Electrons4 Electrons7 Electrons35 Electrons
33 Bohr Models of the Atoms Each atom has shells in which the electrons can fit.1st Shell: fills to 2 electrons2nd Shell: fills to 8 electrons3rd Shell: fills to 18 electrons4th Shell: fills to 32 electronsStart filling the smallest/closest shell first.
34 REVIEWDraw a Bohr Atom Model of Hydrogen, Carbon, and Oxygen on the back of your worksheet.Which subatomic particles belong in the nucleus?Which subatomic particles belong on the rings?What is the difference between ‘ground state’ and ‘excited state’ of an atom?