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Periodic Table Unit John Newlands John Newlands organized his known elements by atomic mass. In studying the elements, he found the chemical/physical properties repeat every 8 elements. Law of the Octaves Dmitri Mendeleev • Mendeleev noticed that when the elements were arranged in order of increasing atomic mass, certain similarities in their chemical properties appeared at regular intervals. • Repeating patterns are referred to as periodic. • Mendeleev created a table in which elements with similar properties were grouped together—a periodic table of the elements Dimitri Mendeleev Columns of elements with similar properties Rows of elements with similar properties In columns by increasing atomic mass In rows by increasin g atomic mass Predicted elements before they were actually discovered Omnipotent? Genius? ..or Astute? Henry Moseley The physical and chemical properties of an element is a function of their atomic number Periodic Law When arranged accordingly similar properties appear at regular intervals Periodicity Actually arranged by the number of protons in the nucleus or atomic number The Modern Periodic Table The Periodic Table is an arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group. A vertical column in the periodic table is called a group or family. Elements have similar chemical properties due to their valence electrons, so elements in the same group/family have the same number of valence electrons A horizontal row in the periodic table is called a period. Elements in the same period/row have the same number of energy levels or orbitals. Valence Electrons The electrons located in the last energy level 8 1 2 3 2 4 5 6 7 Lewis Dot Diagrams • Diagram showing the valence e- in an atom H 1 valence e- N 5 valence e- Mg 2 valence e- S 6 valence e- e- I 7 valence e- Xe 8 valence e- Al C 3 valence 4 valence e- Divided into: Four blocks: (s, p, d and f) Four Regions: (metals, nonmetals, metalloids, noble gases) Modern Periodic Table Main group elements are in the s & p blocks – electron configurations of main group elements are regular & consistent Properties Metals •Malleable •Ductile •Conductive (heat and electricity) •Lustrous (shiny) •Usually solids at room temperature Modern Periodic Table Non-Metals Properties •Non-conductive (heat and electricity) •Usually gases or brittle solids at room temperature •Bromine is the only liquid at room temperature Modern Periodic Table Metalloids Properties •Semi-conductive (heat and electricity) •Display properties of metals and nonmetals Modern Periodic Table Main Group Noble Gases – Group 18 (8A) Properties Ar (1894) He (1895) Ne (1898) Kr (1898) Xe (1898) Rn (1900) •Once thought to be Inert or chemically unreactive •Full set of electrons in outer shell •Low reactivity infers that the full outer shell is most stable *synthetic Modern Periodic Table Main Group Halogens – Group 17 (7A) Properties Cl (1774) I (1811) Br (1826) F (1886) *At (1940) •Highly reactive group of nonmetals •React with most metals to produce salts- “salt makers” •When they react, gain single electron to form full outer shell *synthetic Modern Periodic Table Main Group Alkali Metals (Group 1) Na (1807) K (1807) Li (1817) Cs (1860) Rb (1861) *Fr (1939) Properties •Extremely reactive •React with water to make alkaline solutions (basic) •Never found as pure elements due to their high reactivity •Readily give up their single valence electron to form stable noble gas configuration Modern Periodic Table Main Group Alkaline Metals Sr (1789) Be (1798) Mg (1808) Ca (1808) Ba (1808) Ra (1898) Properties •Less reactive than alkali metals, yet still very reactive and found as compounds in nature •Readily lose 2 valence electrons to form stable noble gas configuration ions Modern Periodic Table Transition Metals Properties •Called d-block elements •Less reactive metals than alkali and alkaline earth metals •Members in each group do not have identical outer shell configurations •Good conductors of heat/electricity. Malleable and ductile Modern Periodic Table Lanthanides Properties •Called f-block elements •Lanthanides follow element lanthanum •Actinide follow element acintium Actinides Modern Periodic Table Hydrogen (1766) Properties •Highly reactive •Non-metal •Class to itself •Most common element in universe Coloring the Periodic Table Hydrogen – Yellow Alkali Metals – Pink Alkaline Earth – Blue Halogens – Red Noble Gases – Purple Transition – Light Green Other Metals – Dark Green Other Nonmetals- Brown Label Lanthanides & Actinides Create a key for your table (example): Metals Alkali Alkaline Earth Transition Other Periodicity Similar properties appearing at regular intervals 1. 2. 3. 4. 5. 6. Atomic Radius Valence Electrons Ionization Energy Electron Affinity Ionic Radius Electronegativity Atomic Radius – Distance from center of atom to outer electron cloud Atoms become larger as we move from top to bottom as we increase our number of shells. Inner electrons shield outer electrons from the pull. Atoms become smaller as we move from left to right because of the nuclear attractive forces. Atomic Radius Trend Decreasing Radius Increasing Radius Nuclear Attractive Forces & Shielding e- eP+ P+ P+ + P+ P P+ + P+ P+ P e- e- The nucleus (+) pulls the electron (-) close to the core. The further the electron is away from the nucleus, the weaker the nuclear pull. Atomic Radius - Graph All elements prefer a noble gas configuration Elements will either lose or gain electrons to achieve this configuration What would be easier? Gain Lose Gain Gain or 3 1 2 Lose 2 Electrons 4Electrons Electron Electron Electrons Electrons Ion – any element that loses or gains electron(s) 3 Li 6.941 1s22s1 eep+ p p+ + e- Cation Li+ 1s2 = [He] Ion – any element that loses or gains electron(s) 8 O 15.9994 1s22s22p4 eeee- e- O2- ee- + p+ +p p+ p p+ p+ ep+ p+ e- e e Anion 1s22s22p6 = [Ne] Ionization Energy Trend Ionization energy is the energy required to take an electron from an atom or ion. The more energy required, the less likely it will lose eIncreasing I.E. Decreasing I.E. Electron Affinity Trend Electron Affinity is the energy change that occurs when a neutral atom gains an electron The more energy released… more likely it will gain eIncreasing E.A. Decreasing E.A. Ionic Radius Ions of atoms become larger as we move from top to bottom Cations (positive ions) are generally smaller than the neutral atom because they lose an entire valence shell! Ionic Radius Ions of atoms become smaller as we move from left to right Anions (negative ions) are generally larger than the neutral atom. Additional electrons added, but not protons – increasing the Ionic Radius Trend Decreasing Ionic Radius Increasing Ionic Radius e- Electronegativity The ability of an atom to attract electron(s) Na Cl Which atom has more electronegativity? Na e- Cl Electronegativity Trend Increasing Electronegativity Decreasing Electronegativity SUMMARY Group Trends Atomic size generally increases as you move down a group of the periodic table. Why? As you descend, electrons are added to successively higher principal energy levels and the nuclear charge increases. The outermost orbital is larger as you move downward. Periodic Trends Atomic size generally decreases as you move from left to right across a period. Why? As you go across a period, the principal energy level remains the same. Each element has one more proton and one more electron than the preceding element. The electrons are added to the same energy level, causing the increasing nuclear charge to pull them in closer. Trends in Ionization Energy When an atom gains or loses an electron, it becomes an ion. The energy required to overcome the attraction of the nuclear charge and remove an electron from a atom is called the ionization energy. Removing one electron results in the formation of a positive ion with a 1+ charge. Na(g) Na+(g) + e- Summary Paragraph Conclusion 1. Why does atomic radius change as it does? 2. Why does the ionization energy change as it does?