Tuesday October 23, 2012 (Valence Electrons and Electron Dot Notation)

How many valence electrons does an atom need to have a stable configuration? What are the only elements that naturally have a stable electron configuration? How do atoms get a stable electron configuration if they do not naturally have one? Most atoms have stable electron configurations if they have eight valence electrons (called a stable octet.) What would the following atoms have to do in order to get these eight valence electrons? 2 for H, He 8 for all others the Noble gases by chemical bonding sodium Lose 1Los2Lose 3 Lose or gain 4, share Gain 3GaGain 1nada magnesium aluminumsiliconphosphorussulfurchlorineargon L 1 L 2L 3L/G 4G 3G 2G 1nada

Write the electron configuration notation for the following atoms: H, He, Li, C, O, Ne, Na, Cl

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Assignment Currently Open Summative or Formative? Date IssuedDate Due Date Into GradeSpeed Final Day QUIZ 6S310/5 10/26 QUIZ 7S410/12 10/26 Pop Quiz – The Periodic Table and the Periodic Law F410/16 QUIZ 8S510/19 10/2211/2 WS – Valence Electrons and Electron Configuration F510/2210/2410/26 WS – Average Atomic Mass F610/2210/2410/26

The element chlorine has an electron configuration notation of: 1s 2, 2s 2, 2p 6, 3s 2, 3p 5 Chlorine has 7 electrons in its highest energy level (3), 2 in the s sub-level and 5 more in the p sub-level. Chlorine counts all 7 of these valence electrons in its bonding considerations.

For main block (s and p) elements, the valence electrons are the electrons in the outermost s- and p- sublevels. The inner electrons are in filled energy levels and are held too tightly by the nucleus to be involved in compound formation.

The alkali metals of group 1 have 1 valence electron. The alkaline earth metals of group 2 have 2 valence electrons. The elements in the p block (groups 13– 18) have a number of valence electrons equal to their group number minus 10. For example, group 13 has 3 valence electrons, group 14 has 4, etc. In some cases, both the s- and p- sublevel valence electrons of the p-block elements are involved in compound formation. In other cases, only the electrons from the p-sublevel are involved.

Number of Highest Energy Level Electrons (Main Blocks Only)

Electron-Dot Notation Thus far we have seen three different types of notation: isotopic notation electron configuration notation orbital notation 1s 2, 2s 2, 2p 2 _____ _____ _____ _____ _____ 1s 2s 2px 2py 2pz

Electron-Dot Notation Here’s a fourth type of notation: Electron-Dot Notation is an electron-configuration notation in which only the valence electrons of an atom are shown, indicated by dots placed around the element’s symbol. Lower energy level, inner - shell electrons are not shown.

Electron-Dot Notation Example: Carbon Carbon is in group 14 and has four valence electrons. 1s 2, 2s 2, 2p 2 Here’s carbon’s electron-dot notation: C 1.Start with the elemental symbol. 2.In your mind, divide the symbol into quadrants, like a tic-tac-toe grid. 3.Beginning in any quadrant put a dot to indicate a valence electron. 4.Continue in a clock-wise direction, putting one dot in each quadrant before any quadrant gets a second dot. 5.Stop when you have put in the number of dots that correspond to the number of valence electrons that element has. ¢ ¢ ¢ ¢

Electron-Dot Notation Example: Fluorine Fluorine is in group 17 and has seven valence electrons. 1s 2, 2s 2, 2p 5 Here’s fluorine’s electron-dot notation: F 1.Start with the elemental symbol. 2.In your mind, divide the symbol into quadrants, like a tic-tac-toe grid. 3.Beginning in any quadrant put a dot to indicate a valence electron. 4.Continue in a clock-wise direction, putting one dot in each quadrant before any quadrant gets a second dot. 5.Stop when you have put in the number of dots that correspond to the number of valence electrons that element has. ¢ ¢ ¢ ¢ ¢ ¢ ¢

Electron-Dot Notation

Worksheet Electron Dot Notation