2 An atom is the smallest particle into which an element can be divided and still be the same substance.See timeline handout for the development of the model of the atom.Identify atom models of Thomson, Rutherford, Bohr, and the Modern Model.
3 What do I need to know? Know the scientist their contribution to the developing model of an atom (their experiment)their atom model!
4 Structure of the atomThe atom contains a nucleus surrounded by one or more electronsThe nucleus contains protons and neutrons.Draw an atom here(Page 320)
16 Terms to copy in notes:atomic number – the number of protons in the nucleus of an atom.(*The number of protons identifies an element!)atomic mass – the average mass of one atom of an element.atomic mass unit (amu) – a measurement of the mass of one proton or one neutron.
17 Chemical Symbols Hydrogen symbol is H Cobalt symbol is Co A chemical symbol is one or two letter(s) representing an element.If the symbol is one letter, it is a printed capital.Hydrogen symbol is HIf two letters, the first is a printed capital and second is lower case.Cobalt symbol is Co
18 Know the Following Elements! The first 20 elements and symbols, plus 7 others, must be properly identified together.iron coppersilver goldmercury tin leadThe symbols must be written in correct form.Spelling counts!
19 ElectronsElectrons are located in an electron cloud around the nucleus.There are different energy levels (“orbits” in the Bohr model) that electrons fill.1st energy level can hold 2 electrons2nd can hold 8 electrons3rd can hold 18 electrons4th can hold 32 electrons
21 Fe Today’s periodic table is based on atomic number. Each element’s square contains:atomic number (protons)chemical symbolelement nameatomic mass (protons &neutrons)This is an average26FeIron55.847
22 How to find the number of neutrons in an atom Round the atomic mass to the nearest whole number.Subtract the number of protons (atomic number).The difference is the number of neutrons.boron atomic mass (protons + neutrons)roundedatomic number (protons)6 neutrons
24 Practice calculating the number of neutrons in an atom Number a blank sheet of paper 1 to 10.Write the name for each element from the periodic table for elements 1-10.Use the right side of your paper to calculate the number of neutrons for elements 1-10.Write your answer next to the elements name.
25 Gaining or losing a neutron makes an atom an isotope. Isotopes are still the same element, just more or less neutrons.carbon 12has 6 neutrons (always 6 protons)carbon 14has 8 neutrons (always 6 protons)The 12 refers tothe mass number(protons + neutrons)
26 Valence electrons are electrons farthest away Valence electrons are electrons farthest away from the nucleus (outer energy level).- involved with chemical reactions.- gives an atom its chemical characteristics.- can be shared, or transferred.- Atoms with a full valence energy level are most stable (less reactive).
27 hydrogen oxygen carbon neon electron dot diagram – represents the valence electrons of an element.- uses an element symbol surrounded by dots representing valence electrons.H O C Nehydrogen oxygen carbon neon
28 The Periodic Table of Elements Chapter 12 NotesThe Periodic Table of ElementsIn 1869 a Russian scientist Dmitri Mendeleev arranged elements in order of increasing atomic mass, and chemical properties.He used his table to predict properties of elements not yet discovered!
29 Fe Today’s periodic table is based on atomic number! Each element’s square contains:atomic number (protons)chemical symbolelement nameatomic mass (protons &neutrons)This is an average26FeIron55.847
30 An element’s properties can be predicted by its location on the periodic table. Groups or families:vertical columns numbered 1-18.elements have similar propertiesPeriods:across rows numbered 1-7elements have predictably different patterns.
31 Metals Metals are found to the left of the stair step. Physical properties:HardnessShininess (luster)Malleability (pound into shapes)Ductility (drawn out into a wire)Good conductorsMagnetic (Co, Ni, Fe)Mostly solids at room temp.
32 Metals Chemical properties: wide range Some violently react with water (Na, K)Some unreactive (Au, Cr)Some corrode (react slowly with O2 and flake off)Alloys (mixture of metals)bronze (Cu + Sn)stainless steel
33 MetalsElements are increasingly nonmetallic reading left to right.Tend to lose electrons formingpositive ions (1+, 2+)Alkali MetalsGroup 1 (1 valence electron)Most reactive metals!Very soft & shiny
34 Metals Alkaline Earth Metals Group 2 (2 valence electrons) Not as reactive as Group 1 but more reactive than most metals.Fairly hard, grey-white colorGood conductors of electricity
35 Metals Transition Metals Groups 3-12 Fairly stable, react slowly with H2OSimilar reactivity between columnsHard and shinyGood conductors of electricity
36 Metals Lanthanides and Actinides Called rare earth metals Fit in Periods 6 and 7 between alkaline earth metals and the transition metals.Placed below periodic table for convenience.Soft, malleable, shiny, very conductive
37 Nonmetals Located right of the stair step Physical properties: Most are gases at room temp. (low boiling point).dullbrittlelower densitiespoor conductors of heat & electricity
38 Nonmetals Halogen Family Chemical properties: Most readily form compoundsWill take electrons from metals formingnegative ions (1-, 2-)Will also share electronsMany form diatomic molecules (O2, N2, H2)Halogen FamilyGroup 17 (7 valence electrons)Very reactive!Dangerous to humans
39 Nonmetals Noble Gases Hydrogen Group 18 Chemically stable (unreactive) Do not gain, lose, or share valence electronsHydrogenAlone in upper left cornerSimplest elementNot grouped in a family
40 Metalloids Along the stair step (7 elements) Have some properties of metals & nonmetalsUsed to make semiconductors