Trends Review, History of the Periodic Table, Oxidation Numbers

Objective – Today I will be able to: Apply the trends of ionization energy, electronegativity and atomic radius to problem solving. Explain the history of the periodic table. Identify the oxidation numbers for the families of elements on the periodic table. Evaluation/ Assessment – Informal assessment – Listening to group interactions and discussions as they complete the analyzing the periodic trends graphing activity – Formal Assessment – Analyzing student responses to the exit ticket, graphs and periodicity practice Common Core Connection – Build Strong Content Knowledge – Value Evidence – Reason abstractly and quantitatively – Look for and make use of structure

Lesson Sequence Warm – Up Evaluate: Review Chapter 5 worksheet Informal assessment Elaborate: Periodicity Practice – Formal assessment Explain: history of the periodic table and oxidation numbers Elaborate: Practice and Exam Review – Informal Assessment Evaluate: Exit ticket Formal assessment

Warm - Up What is ionization energy? – How does it change down a family? Why does this trend occur? – How does atomic radius change across a period? Why does this trend occur? How does an atomic radius compare to an ionic radius?

Objective Today I will be able to: Apply the trends of ionization energy, electronegativity and atomic radius to problem solving. Explain the history of the periodic table. Identify the oxidation numbers for the families of elements on the periodic table.

Homework Periodic Table (mini-exam) on Thursday and Friday next week STEM Fair – Final Research Paper due Monday December 17 – In Class Presentations Wednesday January 23

Agenda Warm – Up Study guide Review Homework Periodicity Practice Worksheet History of the Periodic Table Notes Oxidation Number Notes Exam Review Exit ticket

Review HW – Chapter 5 Worksheet Discuss answers to selected problems and then turn in

Periodicity Practice Complete Worksheet and Review as a class

History of the Periodic Table and Oxidation Number Notes

Johann Dobereiner (1829) Law of Triads - in triads of elements the middle element has properties that are an average of the other two members when ordered by the atomic weight Example - halogen triad composed of chlorine, bromine, and iodine

John Newlands (1864) Law of Octaves - states that any given element will exhibit analogous behavior to the eighth element following it in the periodic table

Dmitri Mendeleev (1871) Developed the first Periodic Table He arranged his table so that elements in the same column (groups) have similar properties; increasing atomic mass

Dmitri Mendeleev (1871) Broke the trend of arranging elements solely by their atomic mass Wanted to keep elements with similar properties in the same columns Left gaps in his early tables; predicted elements that had not been discovered would fill in those gaps - Ekasilicon  Germanium - Germanium was discovered in 1886

Dmitri Mendeleev (1871)

Henry Moseley (1913) Found a relationship between an element’s X-ray wavelength and it’s atomic number (number of protons) Periodic Law - when elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic (repeating) pattern The periodic law is the basis for arranging elements in the periodic table

Glenn Seaborg He reconfigured the periodic table by placing the actinide series below the lanthanide series Awarded a Nobel Prize in 1951 Element 106, Seaborgium (Sg), is named in his honor

Oxidation Numbers

Remember, most atoms strive to have eight valence electrons (some are satisfied with only two) Atoms will form various bonds by gaining, losing, or sharing electrons, in order to satisfy the Octet Rule

Oxidation Numbers An atom’s electron configuration is used to determine how many electrons need to be gained, lost, or shared Example – Na (11 electrons) 1s 2 2s 2 2p 6 3s 1 – 1 valence electron In order for Na to have eight valence electrons, would it be easier for it to gain 7 electrons, or lose 1? Losing 1 is easier

Oxidation Numbers When Na loses an electron it becomes an Na +1 ion 1s 2 2s 2 2p 6 3s 1 becomes… 1s 2 2s 2 2p 6 – 8 valence electrons Na carries a +1 charge because it has lost an electron, and it now has more positively charged protons than negatively charged electrons

Oxidation Numbers Another Example – Fluorine (9 electrons) 1s 2 2s 2 2p 5 – 7 valence electrons In order for F to have eight valence electrons, would it be easier for it to gain 1 electron, or lose 7? Gaining 1 is easier

Oxidation Numbers When F gains an electron it becomes an F -1 ion 1s 2 2s 2 2p 5 becomes… 1s 2 2s 2 2p 6 – 8 valence electrons F carries a -1 charge because it has gained an electron, and it now has more negatively charged electrons than positively charged protons

Oxidation Numbers There is a fairly consistent pattern to oxidation numbers with families Transition Metals and Inner Transition Metals usually have a varying number of valence electrons Some don’t – Zn +2, Cd +2, Sc +2, Ag +1

Exam Review Complete with the people in your row. If you have questions please ask Ms. Ose

Exit Ticket Which element is more likely to have a higher (more negative) electron affinity, Aluminum or Sulfur? List the oxidation number for the following families – Alkali metals – Alkaline earth metals – Halogens – Noble Gases