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Chapter Three PowerPoint PPT Presentation


0. Chapter Three. Atoms and the Periodic Table. 0. Atomic Theory. All matter is composed of atoms Atoms of each element are unique Atoms are composed of subatomic particles (protons, neutrons and electrons) Atoms combine to form compounds in definite proportions

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Chapter Three

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Chapter Three

Atoms and the

Periodic Table


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Atomic Theory

  • All matter is composed of atoms

  • Atoms of each element are unique

  • Atoms are composed of subatomic particles (protons, neutrons and electrons)

  • Atoms combine to form compounds in definite proportions

  • Chemical compounds undergo changes in composition and identity in reactions, atoms remain unchanged

  • Atoms change identities in nuclear reactions


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Nature of the Atom

  • Atoms are small 10-11 meters

  • 1 Angstrom = 10-10 meters


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Subatomic Particles


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Atomic Number (Z)

  • number of protons in nucleus

  • unique for each element

  • elements placed in periodic table by increasing number of protons

    sodium has 11 protons 11Na

    carbon has 6 protons 6C


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Elements are neutral

Number of positive protons =

Number of negative electrons


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Mass Number (A)

Number of particles in the nucleus

Protons + Neutrons = Mass Number

Protons + Neutrons = Nucleons


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Isotopes

  • Elements may have several different isotopes

  • Same number of protons, different number of neutrons


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Atomic Weight

The average mass number of all the naturally occurring isotopes according to relative abundance.

Lithium is 6.941. There is more lithium-7 than lithium-6


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Electrons in Atoms

  • Energy is quantized vs continuous

    • Quantize = step function

    • Continuous = all values are present

  • Similar to digital vs analog


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Shells, Subshells and Orbitals

  • Shells

    • n = principle quantum number

    • Same as period on periodic table

  • Subshells

    • In each shell s > p > d > f

  • Orbitals

    • 2 electrons per orbital


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Orbitals

  • s subshell – 1 orbital – 2 electrons

  • p subshell – 3 orbitals – 6 electrons

  • d subshell – 5 orbitals – 10 electrons

  • f subshell – 7 orbitals – 14 electrons


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Number of Electrons in Shells

2n2

n is the number of the row in the periodic table


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Aufbau – order of filling

  • 1s2

  • 2s22p6

  • 3s23p63d10

  • 4s24p64d104f14

  • 5s25p65d105f14(5g18)

  • 6s26p66d106f14(6g18)(6h22)

  • 7s27p67d106f14(6g18)(6h22)(7i26)


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Increasing Energy

  • 1s22s22p63s23p64s23d104p6

  • Carbon 6 electrons

    • 1s22s22p2

  • Sodium 11 electrons

    • 1s22s22p63s1


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  • Aluminum – 13 electrons

    • 1s22s22p63s23p1

  • Calcium – 20 electrons

    • 1s22s22p63s23p64s2

  • Iron – 26 electrons

    • 1s22s22p63s23p64s23d6

  • Bromine – 35 electrons

    • 1s22s22p63s23p64s23d104p5


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Using the Periodic Table

  • Lithium – 3 electrons

    • 1s22s1

  • Sodium – 11 electrons

    • 1s22s22p63s1

  • Potassium – 19 electrons

    • 1s22s22p63s23p64s1

    • All end in “ns1” configuration


  • Fluorine – 9 electrons

    • 1s22s22p5

  • Chlorine – 17 electrons

    • 1s22s22p63s23p5

  • Iodine – 53 electrons

    • 1s22s22p63s23p64s23d104p65s24d105p5

    • All end in “ns2np5” configuration


The Periodic Table

  • Classification by Properties

    • Arranged by increasing atomic number

    • Rows=periods, columns=groups (families)

  • Main Group – Representative

    • IA, IIA, IIIA, IVA, VA, VIA, VIIA, VIIIA

  • Transition Metals

    • 10 columns in middle of table

  • Inner-transition Metals

    • 14 columns at bottom of table


  • Elements in same column have similar properties

    • Cu, Ag and Au – shiny metals, malleable, conduct electricity


Names of Families

  • Alkali Metals (IA)

    Na and K

  • Alkaline Earth Metals (IIA)

    Mg and Ca

  • Halogens (VIIA)

    F, Cl, Br and I

  • Noble Gases (Inert Gases) (VIIIA)

    He, Ne, Ar, Kr and Xe


Neighboring Groups

  • Metals

  • Non-metals

  • Metalloids (Semiconductors)


Dot Structures for Atoms

  • Valence electrons for representative elements = group number

  • Octet rule


Noble Gas Shorthand

  • [He] = 1s2

    Li = 1s22s1 or [He]2s1

  • [Ne] = 1s22s22p6

    Na = [Ne]3s1

    Mg = [Ne]3s2

  • [Xe] = 1s22s22p63s23p64s23d104p65s24d105p6

    Ba = [Xe]6s2


  • Location on Periodic Table shows location of last electron in configuration

    • Cs = 6s1

    • Sr = 5s2


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