GENERAL CHEMISTRY 1140

ISOTOPES

IONS

ENERGY

HOW ARE CANAL RAYS PRODUCED?

PERHAPS MOLECULES OF THE RESIDUAL GAS WERE HIT BY CATHODE RAYS??

    M + e-1 ---> M+1 + 2e-1

EXPERIMENTS SHOWED THAT MOLECULES COULD BE IONIZED BY HIGH ENERGY CATHODE RAYS (ELECTRONS)

TO GET A BEAM OF IONS, IONS WERE ACCELERATED BY ATTRACTION TO NEGATIVE PLATE

STREAM OF IONS PASS THROUGH A MAGNETIC FIELD

    CHARGED IONS ARE DEFLECTED BY A MAGNETIC FIELD

BY KNOWING THE MAGNETUDE OF MAGNETIC FIELD, ETC.,

    CAN DETERMINE MASS OF THE ION

THIS INSTRUMENT IS CALLED A MASS SPECTROMETER

    CAN NOW DETERMINE ATOMIC WEIGHTS VERY ACCURATELY THIS WAY

MASS SPECTROMETER ANIMATION

WHEN NEON WAS PLACED IN AN IMPROVED MASS SPECTROMETER

    TWO IONS APPEARED WITH MASSES OF 20 AND 22

    BUT ALL OF THE ATOMS WERE NEON

      CONCLUSION

        ATOMS OF THE SAME ELEMENT CAN HAVE DIFFERENT MASSES

        CALL THESE DIFFERENT ATOMS ISOTOPES

ISOTOPES

ATOMS OF THE SAME ELEMENT WITH DIFFERENT MASSES

    ELEMENT IS DEFINED BY THE NUMBER OF PROTONS

    DIFFERENCE BETWEEN ISOTOPES IS THE NUMBER OF NEUTRONS

      NEON-20
        10 PROTONS
        10 NEUTRONS
        10 ELECTRONS

      NEON-22
        10 PROTONS
        12 NEUTRONS
        10 ELECTRONS

      EVENTUALLY A THIRD ISOTOPE OF NEON WAS FOUND, NEON-21

EXPLAINS WHY RELATIVE ATOMIC WEIGHTS ARE NOT INTEGERS

ISOTOPE NOTATION

ATOMIC NUMBER (Z)
MASS NUMBER (A)

    HOW MANY e, p, and n are in 238U?

HYDROGEN ISOTOPES HAVE SPECIAL NAMES

    DEUTERIUM = 2H OR 2D
    TRITIUM = 3H OR 3T

ALPHA PARTICLE IS HELIUM NUCLEUS 4He+2

    A HELIUM ATOM WITHOUT ANY ELECTRONS!

KNOW THIS TABLE!

IONS

ATOMS HAVE NO NET CHARGE SINCE THEY HAVE THE SAME NUMBER OF ELECTRONS AND PROTONS

    CATHODE RAY TUBES AND MASS SPECTROMETERS DEMONSTRATED THAT ELECTRONS CAN BE REMOVED FROM ATOMS (AND MOLECULES) TO PRODUCE POSITIVE IONS CALLED CATIONS

    CATIONS CAN ALSO BE FORMED IN CHEMICAL REACTIONS

      Na ---> Na+1 (A CATION) + e-1
      Cl + e-1 ---> Cl-1 (AN ANION)

    NOTE THAT THE PRODUCT, NaCl, IS ELECTRICALLY NEUTRAL SINCE THERE IS ONE PLUS ONE CHARGE AND ONE MINUS ONE CHARGE

    GROUP 1 ELEMENTS FORM +1 CATIONS
    GROUP 2 ELEMENTS FORM +2 CATIONS
    GROUP 17 ELEMENTS FORM -1 ANIONS
    GROUP 16 ELEMENTS FORM -2 ANIONS

    THE COMPOUNDS ARE CALLED IONIC COMPOUNDS

ALL OF THESE CHANGES INVOLVE ENERGY

BE SURE THAT YOU UNDERSTAND THESE TYPES OF ENERGY, CAN DEFINE AND IDENTIFY THEM, AND CAN GIVE AN EXAMPLE.

    KINETIC ENERGY
    THERMAL ENERGY
    POTENTIAL ENERGY
    CHEMICAL ENERGY
    ELECTRICAL ENERGY
    RADIANT ENERGY

BE ABLE TO STATE AND USE THE LAW OF CONSERVATION OF ENERGY

      | Chemistry Home | Dr. Sundin Home | sundin@uwplatt.edu |