Ch6CP

Periodic Law : Periodic Law Chapter 6


Slide2 : 1790 Antoine Lavoisier – Compiled a list of known elements – 23 1864 John Newlands – 1st proposed organizational scheme for elements


Slide3 : Dmitri Mendeleev – Russian Chemist who first developed the Periodic Table.


Slide4 : Mendeleev’s Periodic Table – elements are arranged according to increasing atomic mass 1st Draft Version of Mendeleev’s table Lothar Meyer very shortly after Mendeleev came to the same conclusion


Slide6 : In 1913 Henry Moseley conducted X-ray experiments on elements. The outcome of his work was the introduction of the atomic number. It was found that if Mendeleev's table was ordered by atomic number instead of atomic mass the inconsistencies in the table were eliminated. This is the blueprint for the modern periodic table.


Slide7 : Periodic Law – The physical and chemical properties of the elements are periodic functions of their atomic numbers. Periodic Table – An arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same group.


Slide8 : The Modern Periodic Table Groups or families – columns in the Periodic Table Periods – Rows in the Periodic Table Representative Elements – Groups IA – 8A (ROSS) or Groups 1, 2, 13-18 ROSS. Transition Elements – Group B elements (Groups 3-12 to the stairstep) Inner Transition elements – Bottom two rows Metals – Left of the Stairstep Nonmetals – Right of the Stairstep Metalloids – on the stairstep


Slide9 : Alkali Metals – Group 1 Alkaline Earth Metals – Group 2 Halogens – Group 17 Noble Gases – Group 18


Slide11 : S block P block D block F block


Slide12 : Section 2 The special case of hydrogen and helium. Hydrogen has a 1s1 configuration. Although it is an s1 configuration, it is very different from the alkali metals. Helium has a 1s2 configuration, but is not at all like the alkaline earth metals of group II. For helium the energy level is filled just like the other noble gases of group 18. The s and p blocks make up the Main Group Elements (Representative elements). The d block makes up the Transition Elements (or Transition Metals). Transition Metals have typical metal properties – good conductors of electricity and high luster The f block makes up the Inner Transition Elements – The Actinides and the Lanthanides.


Slide14 : Electron Configuration and Periodic Trends Atomic Radii – The size of an atom – one half the distance between the nuclei of two identical atoms bonded together


Atomic Radii : Atomic Radii Decreases as you go across a period due to the added positive charge to the nucleus. Increases down a group due to the “shielding effect” caused by the addition of new energy levels. The inner energy levels act in a way to shield the attractive charges of the nucleus for the outer electrons.


Slide16 : Ionization Energy – the energy required to strip away an electron from an atom A + energy  A+ + e- Ion – atom or group of atoms that have a positive or negative charge. Ionization – the process that results in the formation of an ion Ionization energy generally increases as you go across a period. Alkali Metals have a very low ionization energy….. Why?????? Halogens have a very high IE…why???? Ionization energy generally decreases as you move down a group First Ionization Energy IE1 – is the amount of energy needed to remove a first electron. Second Ionization Energy IE2 – is the amount of energy needed to remove a second electron,


Slide19 : Electron Affinity – the energy change that occurs when an electron is acquired by a neutral atom. A + e-  A- + energy Period Trends – generally decreases as you move across a period. Group trends – generally increases as you go down a group. Ionic Radii – The size of the resulting ion. Cation – positively charged ion resulting from the loss of one or more electrons (metals) Anions – negatively charged ion resulting from the gain of one or more electrons (nonmetals) Period Trend – generally decreases from groups 1-14. Large jump in size in group 15, then continues to decrease to group 18. Group trend – increases down a group due to the “shielding effect”


Slide20 : Valence Electrons – the electrons available to be lost, gained, or shared in the formation of chemical compounds. Electrons in the outer energy level. Group 1 – 1 valence electron Group 2 – 2 valence electrons Group 13 – 3 valence electrons Group 14 – 4 valence electrons Group 15 – 5 valence electrons Group 16 – 6 valence electrons Group 17 – 7 valence electrons Group 18 – 8 valence electrons (except helium)


Slide22 : Electronegativity – measure of the ability of the atom in a chemical compound to attract electrons. “Electron Hunger” Period Trend – increases across a period Group Trend – decreases down a group


Slide23 : Elemental Stars Hydrogen – most abundant element in the universe. Magnesium – epsom salt – magnesium sulfate. Flammable metal structural supporting element in the chlorophyll molecule in plant leaves. Calcium – essential for healthy bones and teeth Barium – x-rays of the GI tract Iron – major structural supporting element in hemoglobin molecule in the blood – red blood cells steel Gold – most malleable and ductile substance -1 oz. (28 gram) mass can stretch out to a distance of over 50 miles and pounded to an area of 300 ft2 Silver – best conductor of electricity Aluminum – most abundant metal in the earth’s crust.


Slide25 : Carbon – 3 forms of pure carbon (allotropes – different forms of the same element) Diamond Graphite Buckminsterfullerenes – “Bucky balls” Silicon – important semiconductor – second most abundant element in the earth’s crust Tin – toothpaste – tin fluoride (stannous fluoride Lead – poisonous metal which causes brain damage Nitrogen – most abundant element in the air. Phosphorous – energy element in living things.


Slide27 : Oxygen – most abundant element in the earth’s crust – 2 allotropes: oxygen (O2) and ozone (O3) Sulfur – important in the manufacture of rubber – uniquely mined- sulfur deposits heated with super-hot water and molten sulfur pumped to the surface. Fluorine – added to drinking water to kill germs which cause tooth decay. Chlorine – added to water to kill bacteria Iodine – antiseptic which sublimates. Tincture = dissolved in alcohol Helium – second most abundant element in the universe Neon – lights


Slide29 : Argon – fluorescent bulbs Radon – second leading cause of lung cancer. Naturally occurring.