Dimitri MendeleevDimitri Mendeleev—published his periodic table in 1869 according to similarities based upon atomic mass; applied “eka” to the missing element names
Lothar MeyerLothar Meyer—arranged the elements according to their atomic volume and had a similar periodic table to Mendeleev’s just too late
Henry MoseleyHenry Moseley—student of Rutherford who used X-ray diffraction to prove atomic charge and thus atomic number and suggested arranging in order of increasing atomic number; died in 1915 at the age of 27
An Element on Its Own: Hydrogen nonmetal highly reactive most abundant in the universe
Group 1 (IA) Elements: The Alkali Metals soft (can be cut with a dull knife) highly reactive (especially with water) make basic solutions in water good conductors of electricity (Na is used in street lights) have one valence electron
Group 2 (IIA) Elements: The Alkaline Earth Metals harder than Alkali Metals reactive (but not as reactive as Alkalis) make basic solutions in water found in compounds with structural integrity (emeralds, aircraft, marble) have two valence electrons
Groups 3-12 (B) Elements: The Transition Metals harder than Groups 1 & 2 Metals not very reactive have varying properties most are good conductors all are solid at RT except ??? all are natural except Tc
Lanthanide & Actinide Series: The Inner Transition Metals Lanthanides are shiny and reactive –some are useful: Nd in magnets Actinides all have at least one radioactive isotope –transuranium elements are Atomic #93 and up and are all synthetic and radioactive
The Metalloids B, Si, Ge, As, Sb, Te semiconductors—means that sometimes they conduct and sometimes they insulate
Group 17 (VIIA) Elements The Halogens most reactive nonmetals combine easily with metals to form salts—”halogen” means “salt- former” consist of two solids, one liquid, and two gases at RT have seven valence electrons
Group 18 (VIIIA) Elements The Noble Gases virtually nonreactive nonmetals stable happy valence levels (2 valence electrons in He, and the rest have 8)
Atomic Radius Measured from the centers of two atoms in a diatomic molecule. Rb —distance/2= 0.248nm
Atomic Radius Shielding Effect—the reduction of the attractive force between a nucleus and its outer electrons due to the blocking effect of inner electrons
Atomic Radius As you move across a period, more electrons are added to the same energy level. As you move down a group, more electrons are added to farther and farther away energy levels. THUS…
Atomic Radius Decreases going across a period Increases going down a group
Ionization energy the energy required to remove an electron from an atom or an ion— measured in kJ/mol As you move across a period, the size gets smaller thus the electrons are held more tightly by the nucleus As you move down a group the electrons are farther away from the nucleus and are not held as tightly Thus…
H—1312kJ/mol He—2300kJ/mol K—420kJ/mol Ionization Energy Increases going across a period Decreases going down a group
Electronegativity the ability of an atom in a molecule to attract electrons to itself As you move across a period, there are more and more electrons in the same energy level getting closer to a noble gas As you move down a group, the electrons become farther away from the nucleus Thus…
H—2.1 F—4.0 Fr—0.7 Electronegativity Increases going across a period Decreases going down a group
Electron Affinity The energy change associated with the addition of an electron to a gaseous atom— measured in kJ/mol As you move across a period, there are more and more electrons in the same energy level getting closer to a noble gas As you move down a group, the electrons become farther away from the nucleus Thus…
H= -73kJ/mol F= -329kJ/mol Cs= -45kJ/mol Electron Affinity Increases going across a period Decreases going down a group
Trendy Practice Arrange the following elements in order of increasing atomic size: chlorine, oxygen, fluorine, polonium Arrange the following elements in order of increasing ionization energy: boron, helium, lithium, nitrogen F
Trendy Practice Arrange the following elements in order of decreasing electronegativity: carbon, fluorine, francium, lithium Arrange the following elements in order of increasing electron affinity: cesium, potassium, rubidium, sodium F>C>Li>Fr Cs
Natural Elements are atomic numbers 1-92, excluding 43, Tc three other elements occur so infrequently in nature that they are almost considered unnatural…Pr, At, and Fr are made in stars and result from the violent reactions that occur… the left over stuff makes up all of the naturally occurring elements
Fusion Reactions 1º source of energy 4 H nuclei fuse to form 1 He nucleus mass of the He nucleus < mass of the 4 H nuclei…that means mass was not conserved!!!
Nuclear Fusion Primary fusion reaction in stars 4 H He ? energy E = mc 2
Fusion Reactions Thus, magically, mass was exchanged for energy following the concept put forth in E=mc 2 The He nuclei will then fuse to form all of the other elements that are naturally occurring.
Fusion Reactions A star dies when it no longer has the fusionable stuff to make new elements. Planets result when lots of dead stars come together as one big blob of all of those fun elements.
Man-made fusion reactions were first performed in the 1950’s and resulted in the Hydrogen-bomb cannot be contained in any physical container due to the high heat (>20 million ºC); so must be contained in a magnetic bottle
Fission reactions allow us to make new elements by hitting existing elements with really fast particles this violent act results in the breaking apart of the original element or the absorption of the really fast particle This was first done using those alpha-particles that Rutherford used.
Fission reactions What is the missing particle? Lawrence (as in Lr) developed the 1st cyclotron in Frédéric and Irène Joliet-Curie were the first to make normally stable isotopes radioactive by bombardment in early 1930’s N He 1 1 H + ?
Fission reactions Then truly synthetic elements (those that did not previously exist) were made. The first was ???
Fission reactions (Tc, in particular) In 1937 technetium was created by bombarding molybdenum targets with deuterons (particles consisting of a p + and a n). Because technetium is not part of the decay series of any naturally radioactive element, scientists had thought that technetium does not occur in nature.
Fission reactions (more on Tc) In 1988, however, minute quantities of it were detected in ore from a deep molybdenum mine in Colorado.
Fission reactions Up to atomic number 100, they are made by firing nuclear bullets at existing nuclei to force them to become new elements
Fission reactions Nuclear Bullets –protons –neutrons –alpha particles (really just He nuclei) –beta particles (really just electrons)
Synthetic Elements Atomic #’s 101 and higher are made by using whole nuclei of heavier elements (heavier than He) at existing elements C + Cm No + 2 n
Things to ponder for your quiz 1.The guys and what their tables were based upon 2.Properties of elements in specific groups 3.Atomic radii 4.Ionization energy 5.Electronegativity 6.Electron affinity
Things to ponder for your quiz 7.Fusion & fission reactions 8.Synthetic elements