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SCN 2D – Valence Electrons

SCN 2D – Valence Electrons. Oct 11, 2008. Valency. Valence shell – the outer most shell (energy level) on an atom Valence electrons – the electrons in the valence shell (diagram). Why are valence electrons important?. All atoms want to reach the ‘stable 8’

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SCN 2D – Valence Electrons

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  1. SCN 2D – Valence Electrons Oct 11, 2008

  2. Valency • Valence shell – the outer most shell (energy level) on an atom • Valence electrons – the electrons in the valence shell (diagram)

  3. Why are valence electrons important? • All atoms want to reach the ‘stable 8’ • (or stable 2 for smaller elements H, Li, Be) To do this they can LOSE, GAIN or SHARE their valence electrons to be like their closest noble gas * ONLY valence electrons can be lost, gained or shared

  4. Why are valence electrons important? • Elements in the same group have similar chemical properties because of their number of valence electrons • Knowing the number of electrons in the outer shell helps us: 1) predict formation of compounds 2) write chemical formulas 3) name compounds

  5. Alkali Metals Rx with Water • http://www.youtube.com/watch?v=m55kgyApYrY

  6. E- Dot Diagrams/Lewis Dot Diagrams • Modification of a B-R diagram so that we can focus on the valence e- and reactions

  7. Steps.... • Write the element symbol and note its group number 2) add valence e- 1 side at a time starting at 12 o’clock (examples on board)

  8. Ions • Making Ions Ion: an atom with a charge (+ve or –ve; p+ does not = e-) Atoms can LOSE, GAIN or SHARE valence electrons (today we will focus on losing or gaining)

  9. Atoms the LOSE electrons • Become positively charged (#p+ > #e-) • Called CATIONS (because cats are positive ) • Metals become cations

  10. Atoms the GAIN electrons • Become negatively charged (#p+ < #e-) • Called ANIONS • Non-metals become anions • (examples on board)

  11. Ionic Bonds • Formed between metals and non-metals • Oppositely charged ions attracted to one another and combine to form NEUTRAL molecules • (examples on board)

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