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Periodic Table

Periodic Table. Section 18.3. Periodic Table. Periodic- Repeated in a pattern Elements are ordered by: increasing atomic number changes in physical & chemical properties Mendeleev- Ordered elements by atomic mass

shelley-whitney
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Periodic Table

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  1. Periodic Table Section 18.3

  2. Periodic Table • Periodic- Repeated in a pattern • Elements are ordered by: • increasing atomic number • changes in physical & chemical properties • Mendeleev- Ordered elements by atomic mass • Left blank places in his table to line up elements according to their properties • Elements were later discovered and fit into the places he left blank

  3. Mendeleev

  4. Periodic Table • Moseley- organized elements by atomic number rather than atomic mass • Same arrangement as today • Groups/Families- vertical columns of the periodic table • Rows of Periodic Table- periods • Electrons • Around the nucleus in an electron cloud • Energy levels dictate location of electrons • Closer to nucleus = less energy • Fill energy levels from inner to outer levels

  5. Electrons • Electrons in outer shell – determine chemical properties of elements • Complete outer shell- needs 8 electrons to be stable • Energy levels and # of electrons in each: • Level 1 Holds 2 • Level 2 Holds 8 • Level 3 Holds 18 • Level 4 Holds 32

  6. Energy levels of electrons • Sublevel # e in sublevel Shape • s 2 sphere • p 6 dumbbell • d 10 double dumbbell • f 14 complex • http://library.thinkquest.org/3659/structures/shapes.html

  7. Energy levels of electrons • Level 1 s 2 electrons • Level 2 s & p 2 + 6 = 8 electrons • Level 3 s, p, d 2 + 6 + 10 = 18 e- • Level 4 s,p,d,f 2 + 6 + 10 + 14 = 32 e- • Valence Electrons • Group 1A – 8A have 1-8 valence electrons

  8. Periodic Table, Valence electrons, and Diatomics

  9. Dot Diagrams • Electron dot diagram (or Lewis dot diagram) - A symbol of an element surrounded by dots to represent electrons in the outer energy level • First 2 electrons go together • Next electrons go one on each side, then start to double up

  10. Valence electrons • http://www.ausetute.com.au/lewisstr.html • Properties of elements in the same group- similar due to same # of valence electrons • Alkali metals- group 1A- very reactive metals • Alkaline metals- group 2 A- less reactive than alkali • Halogens- group 7A • Likely to react with Alkali metals- group 1A

  11. Arrangement of Periodic Table • Noble Gases- group 8A- not reactive- don’t form compounds

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