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CHANCE FAVORS THE WELL PREPARED.

CHANCE FAVORS THE WELL PREPARED. REVIEW THREE SUBATOMIC PARTICLES DETERMINE BEHAVIOR. 1 amu = 1.66 x 10 -24 gram. Atoms are very small. Diameters are on the order of 0.1 nanometer (10 -9 meters). Sometimes, the unit Angstrom is used. 1 Angstrom = 10 -10 meter = 0.1 nm

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CHANCE FAVORS THE WELL PREPARED.

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  1. CHANCE FAVORS THE WELL PREPARED.

  2. REVIEW THREE SUBATOMIC PARTICLES DETERMINE BEHAVIOR. 1 amu = 1.66 x 10-24 gram

  3. Atoms are very small. Diameters are on the order of 0.1 nanometer (10-9 meters). Sometimes, the unit Angstrom is used. 1 Angstrom = 10-10 meter = 0.1 nm Atomic diameters range from 1 to 5 Angstroms. Silicon atoms on a surface as imaged using scanning tunneling microscopy.

  4. ALL ATOMS OF THE SAME ELEMENT HAVE THE SAME NUMBER OF PROTONS IN THE NUCLEUS. Z = # protons = atomic number = # electrons A = atomic mass = # protons + # neutrons ATOMS OF A SPECIFIC ELEMENT THAT HAVE DIFFERENT NUMBERS OF NEUTRONS ARE CALLED ISOTOPES.

  5. SOMETIMES, THE ISOTOPES WILL BE REPRESENTED BY THE SYMBOL FOR THE ELEMENT PRECEDED BY A SUPERSCRIPT REPRESENTING THE ATOMIC MASS AND A SUBSCRIPT REPRESENTING THE ATOMIC NUMBER. TAKE THE MOST COMMON ISOTOPE OF CARBON: 126C All of the isotopes of carbon are given below:

  6. The first shell (n=1) can only hold 2 electrons, so there are only 2 elements in the first period. The maximum number of electrons in an outer shell other than the first is 8. 2 electrons in the first shell or 8 electrons in any other outer shell represent a very stable configuration. This is called the octet rule. This will be very important when we talk about chemical bonding. Quantum theory talks about why electron shells and subshells fill the way they do.

  7. THE IDEA OF A PERIODIC TABLE WAS DEVELOPED BY SEVERAL SCIENTISTS AT ABOUT THE SAME TIME. MENDELEEV WAS THE FIRST TO PUBLISH IN 1869. HE SUGGESTED THAT SUCH A TABLE COULD BE CONSTRUCTED BY ARRANGING THE ELEMENTS IN ORDER OF INCREASING ATOMIC MASS. LATER, SCIENTISTS REALIZED THAT IT SHOULD BE IN ORDER OF INCREASING ATOMIC NUMBER.

  8. PERIODIC LAW – WHEN ELEMENTS ARE ARRANGED IN ORDER OF INCREASING ATOMIC NUMBER, THERE IS A PERIODIC REPETITION OF THEIR PHYSICAL AND CHEMICAL PROPERTIES. NOW, IN THE PERIODIC TABLE, THE VERTICAL COLUMNS ARE CALLED FAMILIES OR GROUPS. THE HORIZONTAL ROWS ARE CALLED PERIODS.

  9. ALL OF THE ELEMENTS IN A GIVEN COLUMN OR FAMILY WILL HAVE SIMILAR OUTER ELECTRON CONFIGURATIONS. FOR EXAMPLE, TAKE THE 1ST COLUMN – THE ALKALI METALS. H – 1s1 Li – 2s1 Na – 3s1 K – 4s1 Rb – 5s1 Cs – 6s1 ALL HAVE 1 ELECTRON IN THE OUTER SHELL.

  10. THE OUTER SHELL IS IMPORTANT. IT IS THE ELECTRONS IN THE OUTERMOST SHELL THAT WILL BE INVOLVED IN CHEMICAL REACTIONS. THEY ARE CALLED VALENCE ELECTRONS. THEY WILL FORM CHEMICAL BONDS THROUGH LOSS, GAIN, OR SHARING.

  11. TAKE ANOTHER EXAMPLE – THE SECOND COLUMN, THE ALKALINE EARTH METALS: Be – 2s2 Mg – 3s2 Ca – 4s2 Sr – 5s2 Ba – 6s2 THEY ALL HAVE TWO ELECTRONS EACH IN THEIR OUTER SHELLS.

  12. OR, TAKE GROUP 7A, THE HALOGENS. THEY ALL HAVE 7 ELECTRONS IN THE OUTER SHELL. F – 2s22p5 Cl – 3s23p5 Br – 4s24p5 I – 5s25p5 At – 6s26p5 THE GROUP NUMBER FOR THE A GROUP ELEMENTS WILL TELL YOU HOW MANY ELECTRONS ARE IN THE OUTER SHELL – VALENCE ELECTRONS.

  13. THE ELEMENTS ARE GROUPED ACCORDING TO ELEMENT TYPE AS WELL – METALS, NONMETALS, AND METALLOIDS. THE METALS TO THE LEFT OF THE PERIODIC TABLE, STARTING WITH THE LIGHT BLUE, DARK BLUE, BLUE-GRAY, AND ORANGE. THE NONMETALS ARE TO THE RIGHT OF THE PERIODIC TABLE AND ARE GREEN, YELLOW, AND ORANGE. THE METALLOIDS ARE IN PURPLE.

  14. METALS ARE ALL SOLIDS, WITH ONE EXCEPTION (MERCURY), AT ROOM TEMPERATURE. THEY HAVE A SHINY SURFACE WHEN FRESHLY CUT OR POLISHED. THEY ARE GOOD CONDUCTORS OF HEAT AND ELECTRICITY. MOST CAN BE PULLED INTO WIRES (DUCTILE) OR ROLLED INTO SHEETS (MALEABLE).

  15. NONMETALS ARE BRITTLE SOLIDS OR GASES AT ROOM TEPMERATURE. BROMINE IS THE ONLY LIQUID. THEY ARE NOT GOOD CONDUCTORS OF ELECTRICITY OR HEAT (WITH THE EXCEPTION OF CARBON). METALLOIDS HAVE PROPERTIES BETWEEN THOSE OF METALS AND NONMETALS. SILICON WOULD BE A GOOD EXAMPLE. IT LOOKS LIKE A METAL, BUT IT IS BRITTLE.

  16. THE ELEMENTS IN DARK BLUE IN THE CENTER OF THE PERIODIC TABLE ARE CALLED THE TRANSITION METALS. AS YOU MOVE ACROSS A PERIOD, ELECTRONS ARE BEING ADDED TO THE d SUBSHELLS. FOR EXAMPLE, STARTING WITH ELEMENT 21, SCANDIUM, AND MOVING ACROSS TO ZINC, ELECTRONS WOULD BE ADDED TO THE 3d SUBSHELL.

  17. IN THE LANTHANIDE SERIES (STARTING WITH ELEMENT 58) ELECTRONS ARE GOING INTO THE 4f SUBSHELL. THE LANTHANIDE SERIES ELEMENTS ARE SOMETIMES REFERRED TO AS THE RARE EARTH ELEMENTS. IN THE ACTINIDE SERIES (STARTING WITH ELEMENT 90) ELECTRONS ARE GOING INTO THE 5f SUBSHELL.

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