2 Atoms, Elements & the Periodic Table Describe the structure & parts of an atom.Identify the properties of an atom.Interpret information on a periodic table to understand how elements are grouped.
3 What are the elements made of? Element-the simplest pure substance.Elements are made of atoms, and each element’s atoms are unique to that elementAtoms-the basic building blocks of all matter. They are the smallest particles into which an element can be divided and still be the same substance.Atoms are made of 3 types of particles-protons, neutrons and electrons
11 Ernest Rutherford - 1909 Discovered the nucleus Nucleus Small tiny very dense center of atomsWhere most the atoms mass is locatedAtoms are mostly empty space where electrons are foundConducted the Gold Foil experiment
15 Most Recent Atomic Theory Schrodinger and HeisenbergElectron paths cannot be predicted.Electrons are likely to be found in regions around the nucleus called electron clouds.Called the electron cloud model.
16 Recent Discoveries Chadwick 1932-Discovered that neutrons exist in the nucleus of atomsNeutrons have no charge and the mass equal to protons and help to stabilize the atomGell-Mann1969-Subatomic particles are made of smaller particles called quarks
18 PERIODIC TABLE =ORGANIZED ELEMENTS Elements are:PURE-Made of like atoms of that elementIdentified by it’s atomic number (# of protons)Arrangement of electrons determines the elements properties (such as conductivity and reactivity).
19 The Element Song Link to video Select broadband player.
20 The Structure of an Atom Protons – POSITIVE charged particles inside the nucleus (center).Neutrons – neutral particles inside the nucleus that have NO CHARGE!Electrons – NEGATIVE CHARGED particles in atoms found around the nucleus.
21 Atomic Particles Location Charge Mass Protons Nucleus + positive Heaviest particleNeutronsO NeutralSimilar to a proton but carry no chargeElectronsOrbiting outside the nucleus in electron clouds- NegativeLightest particleSmallest part of an atom
22 Outside the nucleusCan be called a electron cloud, shell, energy level, orbit or ringArea outside the nucleus where electrons are found1st cloud=2 electrons2nd cloud=8 electrons3rd cloud=18 electrons
26 Energy Levels - Electron Clouds Regions around the nucleus where electrons are arranged.Electrons further away from the nucleus have more and more energy.Each level or cloud can hold a specific # of electrons.1st level - 2 electrons2nd level - up to 8 electrons3rd level-up to 18 electrons
27 Valence ElectronsThe electrons in the outermost energy level (electron cloud).Very important because they determine how an element will react with other substances
29 Atomic Number5B10.81BoronEquals the number of protons inside the nucleus of the atom.Atomic Number=Number of Protons=the number of electronsDetermines the element.All atoms of an element have the same atomic number.No two elements have the same atomic number.
30 Symbol B All elements have their own unique symbol 5B10.81BoronAll elements have their own unique symbolSymbols can be one or two lettersThe first letter is always a capital letterThe second is always a lower case letterSymbols don’t always match their English word bc most are from Latin or Greek roots.Example: Fe=Iron (English) Ferrum (Latin)
31 Mass Number5B10.81BoronThe total number of protons and neutrons in an atoms nucleus.Number under the element symbolProtons + Neutrons = Mass NumberPractice: If an atom has 12 protons, 14 neutrons and 12 electrons, what is its mass number?Practice onlineAns: 12 protons + 12 neutrons=24
32 Atomic Mass Unit - amuUnit of measurement for the mass of subatomic particles.1 amu = 1.7 X They are TEENY TINY!!!gramsProton = 1 amuNeutrons = 1 amuElectrons = almost zero (TINIEST particle with the least mass)Most of the mass is in the nucleus with protons and neutronsOtherwise atoms are mostly EMPTY SPACEAmu will be addressed in slide 14, but you can refer back to this slide for review at the end
33 Atomic Mass Refers to the weight of the atom. Atomic Mass= Protons + NeutronsNever negativeMass
34 The Charge of an atom To find the charge of an atom- Find the number of protons (+)Find the number of electrons (-)Represent the electrons as a negative numberAdd the protons and electrons to find the chargeEx: Calcium atom has 12 protons and 10 electrons. What is the charge of this atom?Answer 12 proton + 10 electrons(-10)= +2This atom would be positive (+)Be sure to reinforce that these are not neutral atoms. When students look at their periodic table, they can assume all of the elements’ atoms are neutral unless given additional information. Also point out that the only thing to change the charge is whether the atom has gained or lost electrons, and that the # of protons will always stay the same. The method above is designed to help students avoid thinking “the atom LOST electrons, so it must be negative, “ and lets them use simple math
35 More practice with charge What is the charge of a copper atom with 26 electrons?What is the charge of a Sulfur atom with 18 electrons?29 protons (+) + 26 electrons (-) 29-26=+3 positiveCopper’s atomic # is 29 if students do not have their periodic table16 protons (+) + 18 electrons (-)16-18=-2negative
36 Review Nucleus-contains protons and neutrons Electron Cloud-electrons orbit the nucleusElements are made ofAtoms, which containProtons (+), neutrons (o)and electrons (-)#protons# neutronsMass #
42 Alkaline-Earth Metals Group #2All Metals2 Valence ElectronsVery reactive but less than group #1.
43 Transition Metals Groups # 3-12 All metals 1-2 valence electrons Less reactive than group #2Also contain lanthanide and actinide series (radioactive/unstable).
44 Groups # 13-16Elements change from metals to nonmetals and include the metalloids.Atoms have 10 fewer valence electrons than the group #.Boron Group # valence electronsCarbon Group # valence electronsNitrogen Group # valence electronsOxygen Group # valence electrons
45 Halogens Group 17 All nonmetals 7 valence electrons Very reactive Only need to gain 1 more electron.
46 Noble Gases Group # 18 All nonmetals 8 valence electrons - except helium only has 2.UnreactiveHave a full outer electron cloud (energy level).
47 Hydrogen stands alone 1 valence electron Very reactive Reacts violently with Oxygen under the right conditions.
49 IsotopesAtoms of elements that have the same number of protons (atomic number) but a different number of neutrons inside the nucleus.
50 Ions Charged particles that form during chemical changes. Form when one or more valence electrons are transferred from one atom to another.
51 Ions are Charged! + or -Atoms that lose electrons become positive ions.Atoms that gain electrons become negative ions.Cl gains an electron from Na to form NaCl -Cl ion is negative - more electrons (-)Na ion is positive - more protons (+).