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ELECTRON DOT FORMULAS—HOW DO THEY WORK?. (also known as Lewis dot structures). THE “DOT”. 1) Represents an electron 2) Specifically valence electrons (electrons in the outermost shell). #1. Cs C I. #2. S Ca B. Guess: #3. Sr Cl Xe. Guess: #4.
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ELECTRON DOT FORMULAS—HOW DO THEY WORK? (also known as Lewis dot structures)
THE “DOT” • 1) Represents an electron • 2) Specifically valence electrons (electrons in the outermost shell)
#1. Cs C I
#2. S Ca B Guess: #3 Sr Cl Xe
Guess: #4. O Ba N Guess: #5 Kr Mg P
What are the rules? • 1) Number of dots = last digit of group # • 2) Order of dots: • 3) Why this order? first 2 are “s” electrons; next 6 are “p” electrons: 2 1 X 3 8 6 5 7 4
Guess: #6. F Al Si Guess: #7 Ar Be Na
- 2- - OK, so you think you have it?Try these: Guess#8 Cl- Br- S2- Cl Br S
2- 3- Just one more: Guess #9 O2- N3- Si4+ 4+ O N Si
What are the rules for ions? • 1) Add or subtract the appropriate number of electrons • 2) Place brackets around the Lewis dot structure • 3) Write ion’s charge to the upper right hand corner
Octet Rule • Notice there’s a trend for forming ions • The octet rule states that atoms will form ions by gaining or losing electrons so they will have a “full” valence shell of 8 (an “octet” of) electrons just like a noble gas • Exception: The duet rule is for hydrogen and helium—they obtain a full shell of 2 (a duet of) electrons