Presentation on theme: "Introducing the Elements The Element Song. 1869: Dmitri Mendeleev Russian chemist Arranged elements in tabular form so that elements with similar properties."— Presentation transcript:
1869: Dmitri Mendeleev Russian chemist Arranged elements in tabular form so that elements with similar properties were in the same column When listed in order by mass, elements generally repeat properties in groups of 8 (Law of Octaves)
The First Periodic Table Most tables at the time listed elements by mass Mendeleev also arranged elements by mass, but left several “holes” in his table and occasionally reversed the order of elements to fit the properties of others in that column The “holes” were later filled in with newly discovered elements that had the properties predicted by Mendeleev’s table. The reason for the reversal of elements was explained later by Henry Moseley, who noted that the elements were in order by atomic number (number of protons) rather than by mass
Hydrogen Most abundant element in the universe Why? Makes up most the mass of stars Can be H+ (hydrogen ion) or H- (hydride ion) Used in Fuel Cells: How Stuff WorksHow Stuff Works In Fusion, H is converted to He
Alkali Metals: Li, Na, K, Rb, Cs, Fr Most reactive of the metals, +1 ions Stored under kerosene or mineral oil Na and K most important Na 2 CO 3 and NaHCO 3 two important compounds K is an important plant nutrient (macronutrient) Fertilizers: N-P-K
Total Molar Composition of Seawater (Salinity = 35)   Compone nt Concentration (mol/kg) H2OH2O53.6 Cl − 0.546 Na + 0.469 Mg 2+ 0.0528 SO 2− 4 0.0282 Ca 2+ 0.0103 K+K+ 0.0102 CTCT 0.00206 Br − 0.000844 BTBT 0.000416 Sr 2+ 0.000091 F−F− 0.000068
Alkaline Earth Metals: Be, Mg, Ca, Sr, Ba, Ra Harder, more dense, and less reactive than alkali metals Ca, Sr, and Ba most alike Hard Water: Ca2+ and Mg2+ ions Epsom salt: MgSO 4 Boiler Scale
…..more on the alkaline earths CaCO 3 is limestone becomes marble Limestone is most abundant rock in the earth’s crust CaO “Lime” or “quicklime” CaSO 4 “Plaster of Paris” (building material) Plaster of Paris footprints
Aluminum Group: B, Al, Ga, In, Tl Aluminum by far the most important Third most abundant element in the earth’s crust Important metal: abundant, light weight, strong Al 2 O 3 coating prevents corrosion
Carbon Group: C, Si, Ge, Sn, Pb Very diverse group of elements C is the basis for organic compounds CO 2 and CO 3 -2 inorganic carbon CO 2 one of the earliest gases in the atmosphere Carbon cycling one of the most important Two basic parts: (1) photosynthesis (2) respiration
Disrupting the carbon cycle CO 2 is a greenhouse gas (GWP=1) Increasing concentration by: 1.Burning fossil fuels 2.Removing vegetation Preindustrial 1800: 280 ppm 1959: 316 ppm 2010: 388 ppm 2011: 391 ppm
Growing CO 2 Warms the Earth Greenhouse Effect is essential for Life! –Earth’s radiative balance (solar input vs. IR output) leaves ~ – 20°C Almost all water would be ice everywhere. But Life requires ℓiquid water! –H 2 O(g) and CO 2 absorb outbound IR and reradiate it omnidirectionally. So Earth intercepts ~½ that absorbed IR and gains to +15°C. H 2 O(ℓ) & we exist.
Venus, the Runaway Greenhouse Being closer to the sun, Venus intercepts twice the solar flux of Earth. But it is twice as reflective (albedo), so its temperature would be ~ –29°C. But it’s surface T averages +435°C! 90 atm at the surface, mostly CO 2
Silicon - Si Second most abundant element in the Earth’s crust Found in clay, sand, sandstone, silica rock, quartz, other minerals Many different bonding combinations Is a semiconductor (Silicon Valley)
Tin (Sn) and Lead (Pb) Many Industrial Uses Pb is a “heavy metal” and is toxic to many organs in the human body Impedes the development of the nervous system Taken out of gasoline in the late 1970’s and removed from most paints
Ozone Ozone absorbs much of the radiation between 240 and 310 nm. It forms from reaction of molecular oxygen with the oxygen atoms produced in the upper atmosphere by photodissociation (< 242 nm). O + O 2 O 3
Ozone Depletion In 1974 Sherwood Rowland and Mario Molina (Nobel Prize, 1995) discovered that chlorine from chlorofluorocarbons (CFCs) may be depleting the supply of ozone in the upper atmosphere.
Chlorofluorocarbons CFCs were used for years as aerosol propellants and refrigerants. Mostly = CFCl 3, CF 2 Cl 2. They are not water soluble (so they do not get washed out of the atmosphere by rain) and are quite unreactive (so they are not degraded naturally).
Chlorofluorocarbons The C—Cl bond is easily broken, though, when the molecule absorbs radiation with a wavelength between 190 and 225 nm. The chlorine atoms formed react with ozone: Cl + O 3 ClO + O 2
Chlorofluorocarbons In spite of the fact that the use of CFCs in now banned in over 100 countries, ozone depletion will continue for some time because of the tremendously unreactive nature of CFCs.
Sulfur Sulfur dioxide is a by- product of the burning of coal or oil. It reacts with moisture in the air to form sulfuric acid. It is primarily responsible for acid rain.
Sulfur High acidity in rainfall causes corrosion in building materials. Marble and limestone (calcium carbonate) react with the acid; structures made from them, erode.
Sulfur SO 2 can be removed from flu gases by injecting powdered limestone which is converted to calcium oxide. The CaO reacts with SO 2 to form a precipitate of calcium sulfite. This process = “scrubbing”
Carbon Monoxide Carbon monoxide binds preferentially to the iron in red blood cells. Exposure to CO can lower O 2 levels to the point of causing loss of consciousness and death.
Carbon Monoxide Products that can produce carbon monoxide must contain warning labels. Carbon monoxide is colorless and odorless, so detectors are a good idea.
Nitrogen Oxides What we recognize as smog, that brownish gas that hangs above large cities like Los Angeles, is primarily nitrogen dioxide, NO 2. It forms from the oxidation of nitric oxide, NO, a component of car exhaust.
Photochemical Smog Nitrogen oxides react with water to form nitric acid, contributing to acid rain. Smog also contains ozone, carbon monoxide, hydrocarbons, and particles.
Bonding: Influences Valence Electrons Nuclear Charge Atomic Size/Radius Distance between attractions Screening or Shielding Effect
Radius trends Group trend? Radius increases down a group Why? Adding new energy levels Period trend? Radius decreases across a period Why? Increasing nuclear charge has the effect of pulling electron cloud closer.
Ions and their formation Cations Formed by the loss of electrons Positively charged Usually formed from metals Are always smaller than the atom they are formed from Anions Formed by the gain of electrons Negatively charged Usually formed from nonmetallic elements Are always larger than the atom they are formed from
Ionization Energy The energy required to remove an electron from an isolated, neutral, gaseous atom. First ionization energy – energy required to remove a first electron from an atom. Second ionization energy – energy required to remove a second electron from an atom. Third ionization energy - ???? Etc....
First Ionization energies Group trend – IE 1 decreases down a group. Why? Valence electrons are further from the nucleus and the shielding effect is greater down a group. Shielding effect – occurs when core electrons “shield” or interferes with the attraction that the nucleus has for the valence electrons.
... IE cont.... Period trend – IE 1 is larger as you move across a period, left to right. Why? Atoms are smaller so valence electrons are closer to the nucleus and........ the nuclear charge is greater with no change in shielding effect (electrons are going in the same energy level)
Ionization Energy Increasing Trend Periodic Table
Successive Ionization Energies Where do the largest jumps occur for each Element and why do you think this happens?
Electronegativity A measure of the ability of an atom to attract electrons to itself when bonded to other atoms. Trends in electronegativity are the same as ionization energy and the reasons why are essentially the same too.
Electron Affinity The amount of energy released or gained when an atom receives an electron. When this happens a negatively charged ion, called an anion, forms.
Electron Affinity Notice what groups have (-) negative affinities and what groups have (+) positive affinities (negative values are shown here as above zero.) A negative affinity means energy is released and a positive affinity means that much energy is gained when an atom acquires and electron.
1.Place these elements in order of increasing: Ge, P, N, and Si (a) atomic radius (b) first ionization energy (c) electronegativity 2. Write the core configuration for the following elements: S, Ca, Sn 3.How many valence electrons does each element in #2 have?