Presentation on theme: "Chapter 18—PROPERTIES OF ATOMS AND THE PERIODIC TABLE"— Presentation transcript:
1Chapter 18—PROPERTIES OF ATOMS AND THE PERIODIC TABLE Section—1: STRUCTURE OF THE ATOM
2ATOMIC COMPONETSAn element is matter that is composed of 1 type of atom.An atom is the smallest piece of matter that still retains the property of the element.EXAMPLE—the element silver = ONLY silver atoms; the element hydrogen = ONLY hydrogen atoms
4RUTHERFORD—British physicist—1911 (Majority of atom’s mass in nucleus) ATOMIC MODELSRUTHERFORD—British physicist—1911 (Majority of atom’s mass in nucleus)BOHR—Danish physicist—1913 (Electrons in fixed orbits; nucleus had +p, 0 n
5PROTONS + NEUTRONS = NUCLEUS (+ Charge) ELECTRONS =OUTSIDE THE NUCLEUS (- Charge)Protons=PositiveNeutrons=Neutral (NO CHARGE)Electrons=Negative
6Chapter—18—PROPERTIES OF ATOMS AND THE PERIODIC TABLE Section 2—MASSES OF ATOMS
7ATOMIC MASSThe NUCLEUS contains most of the mass of an atom, because PROTONS AND NEUTRONS are far more massive than electrons.Protons and neutrons are about 2,000 times more massive than an electron.The unit of measurement used for atomic particles is the atomic mass unit or amu.
8ATOMIC MASS UNIT (AMU)The mass of a proton or a neutron is equal to 1 amu.Example---Atomic Mass Unit for CARBONC = 12, BECAUSE6 PROTONS NEUTRONS = 12 amu’s
9PROTONS IDENTIFY THE ELEMENT The number of protons tell you what type of atom you have.Ex. All atoms with 6 protons = Carbon; All atoms with 8 protons = OxygenThe number of protons = the atomic numberCarbon = 6 protons = atomic number is 6Oxygen = 8 protons = atomic number is 8
10MASS NUMBER OR ATOMIC MASS The mass number of an atom is the sum of the number of PROTONS and the number of NEUTRONS in the nucleus of an atom.MASS NUMBER (ATOMIC MASS) = Protons + Neutrons
13NEUTRONSIf you know the mass number (atomic mass) and the atomic number of an atom, you can calculate the number of NEUTRONS.NUMBER OF NEUTRONS = mass number (atomic mass)- atomic numberORNUMBER OF NEUTRONS = BIG - LITTLE
14ISOTOPES Not all atoms of an element have the same number of NEUTRONS. Atoms of the same element that have a different number of neutrons are called ISOTOPES. (Ex. U-235, U-238)
15ISOTOPESEx. CARBON with an atomic mass equal to 12 or carbon-12, is the most common form of carbon.Carbon-12 = 6 protons + 6 neutronsCarbon-14 = 6 protons + 8 neutronsDIFFERENT NUMBER OF NEUTRONS = ISOTOPE 0F CARBON
16AVERAGE ATOMIC MASSThe average atomic mass of an element is the weighted-average mass of the mixture of its isotopes.NOTE—the average atomic mass of an element is close to the mass of its most common isotope.ATOMIC MASS = AVERAGE = MOST COMMON
17CHAPTER 18—PROPERTIES OF ATOMS AND THE PERIODIC TABLE Section 3—THE PERIODIC TABLE
18Dimitri Mendeleev—THE ORIGINAL PERIODIC TABLE LATE 1800’S—RUSSIAN CHEMISTPERIODIC TABLE—BASED ON INCREASING ATOMIC MASSES
19THE ORIGINAL PERIODIC TABLE In the late 1800’s, Dmitri Mendeleev, a Russian chemist, searched for a way to organize the elements in order of increasing atomic masses.On Mendeleev’s table, the atomic mass gradually INCREASES from left to right.
20THE MODERN PERIODIC TABLE If you look at the modern periodic table, you will see several examples, such as COBALT and NICKEL, where the atomic masses DECREASEfrom left to right.In 1913, the work of Henry G.J. Mosely, a young English scientist, led to the arrangement of elements based on their INCREASING atomic numbers instead of atomic masses.
21REGIONS OF THE PERIODIC TABLE--PERIODS The horizontal rows are of elements are called periods. (1-7)The elements INCREASE by 1 PROTON and 1 ELECTRON as you go from left to right in a period.
22REGIONS OF THE PERIODIC TABLE--METALS All elements in blue are METALS—EXS. Iron, zinc, copperMost are SOLIDSALSO:SHINYDRAWN INTO WIRES (DUCTILE)POUNDED INTO SHEETS (MALLEABLE)GOOD CONDUCTORS OF HEAT AND ELECTRICITY
23REGIONS OF THE PERIODIC TABLE--NONMETALS All elements in yellow are NONMETALS—EXS. Oxygen, bromine, carbonMost are GASESBRITTLEPOOR CONDUCTORS OF HEAT AND ELECTRICITYThose elements in green are METALLOIDS—EXS. Boron, silicon---properties of both METALS AND NONMETALS
24REGIONS OF THE PERIODIC TABLE--GROUPS Vertical columns in the periodic table are called GROUPS or FAMILIES, and are numbered 1 through 18.Elements in each group have similar PROPERTIES.GROUP 11—Copper, silver, gold—All shiny metals; All good conductors of electricity and heat.
25What is responsible for the similar properties? ELECTRONSElectrons are located in the electron cloud.Electrons have different amounts of ENERGY within the electron cloud.↑ ENERGY = ↑DISTANCE from the nucleus
27These ENERGY LEVELS (PERIODS) are named using numbers 1-7. ENERGY LEVEL 1 or PERIOD 1—may acquire 2; max number of electrons is 2.ENERGY LEVEL 2 or PERIOD 2—may acquire 8; max number of electrons is 10 ( 2 from period 1 and 8 from period 2).ENERGY LEVEL 3 or PERIOD 3—may acquire 8; max number of electrons is 18 (2 from period 1, 8 from period 2, and 8 from period 3).
28ATOMIC NUMBER = PROTONS = ELECTRONS REMEMBER—that the atomic number is EQUAL to the number of protons in an atom.ALSO—the number of protons is EQUAL to the number of electrons in an atom.
29OUTER ENERGY LEVEL ELECTRONS Elements in the same GROUP have the same number of electrons in their outer energy level.(SAME PROPERTIES)These OUTER ELECTRONS are so important in determining the CHEMICAL PROPERTIES of an element that a special way to represent them has been developed.
30ELECTRON DOT DIAGRAMSAn electron dot diagram uses the symbol of the element and dots to represent the electrons in the OUTER ENERGY LEVEL.ELECTRON DOT DIAGRAMS are also used to show how the electrons in the OUTER ENERGY LEVEL are bonded when elements combine to form COMPOUNDS.
31LONG VERSION—hydrogen, helium—period-1,energy level-1 = 1 ring; hydrogen—atomic number 1= 1 electron; helium--atomic number 2 =2 electrons
32LONG VERSION—lithium, neon—period-2,energy level-2 = 2 rings; lithium—atomic number 3= 3 electrons—max 2 in 1st , 1 in 2nd; neon--atomic number 10 =10 electrons—max 2 in 1st, max 8 in 2nd.
33LONG VERSION—sodium, argon--period-3,energy level-3 = 3 rings; sodium—atomic number 11=11 electrons—max 2 in 1st , max 8 in 2nd, and 1 in 3rd; argon--atomic number 18=18 electrons—max 2 in 1st, max 8 in 2nd, and max 8 in 3rd.
34SHORT-CUT—The elements in GROUP-1 have 1 electron in their OUTER ENERGY LEVEL. This electron dot diagram represents that one electron.
35SHORT-CUT—The elements in GROUP-17, the HALOGENS, have 7 electrons in their OUTER ENERGY LEVEL.
36BONDING—Require complete OUTER ENERGY LEVELS A common property of the halogens, Group-17, is the ability to form compounds with elements from Group-1.Group-1 element, SODIUM, 1e, reactswith Group-17 element,CHLORINE, 7e. (1 + 7=8)
37NOT ALL ELEMENTS WILL COMBINE READILY WITH OTHER ELEMENTS. The elements in Group-18 have COMPLETE OUTER ENERGY LEVELS.This makes Group-18, the NOBLE GASES, relatively unreactive.
38SHORT-CUT—The elements in GROUP-18, the NOBLE GASES, have 8 electrons in their OUTER ENERGY LEVEL.