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Bellwork. Write the electron configurations for magnesium and chlorine. How many electrons do these elements have in their highest energy level?. Valence electrons are the electrons in the highest occupied energy level of an atom.

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bellwork
Bellwork
  • Write the electron configurations for magnesium and chlorine.
  • How many electrons do these elements have in their highest energy level?
slide2
Valence electrons are the electrons in the highest occupied energy level of an atom.

The number of valence electrons largely determines the chemical properties of an element.

slide3
The group number tells you the number of valence electrons.
  • Group 6A = Group 16 = 6 valence electrons
valence electrons
Valence Electrons
  • Applications of Group 4A Elements

Silicon

Carbon

Germanium

slide5
Lewis Dot Diagrams
  • Because valence electrons are so important to the behavior of an atom, it is useful to represent them with symbols.
slide6
A Lewis dot diagram illustrates valence electrons as dots (or other small symbols) around the chemical symbol of an element.
slide7
Each dot represents one valence electron.
  • The element’s symbol represents the core of the atom—the nucleus plus all the inner electrons.
slide9
Lewis Dot Structures for Atoms

See supercool handout

 Classwork- Draw dot structures for the following elements and write which energy level the valence electrons are found in.

1. Hydrogen 2. Helium 3. Sodium 4. Magnesium 5. Aluminum 6. Silicon 7. Phosphorous 8. Oxygen 9. Flourine 10. Sulfur 11. Chlorine 12. Krypton 13. Iodine 14. Arsenic 15. Calcium 16. Tin 17. Xenon

slide10
Noble gases, such as neon and argon, are unreactive in chemical reactions. In 1916, chemist Gilbert Lewis used this fact to explain why atoms form certain kinds of ions and molecules.
  • The octet rule: In forming compounds, atoms tend to achieve the electron configuration of a noble gas.
slide11
Metals lose their valence electrons, leaving a complete octet in the next-lowest energy level.
  • Non-metals gain electrons to achieve a complete octet.
slide13
You can represent the electron loss, or ionization, of the sodium atom by drawing the complete electron configuration of the atom and of the ion formed.
formation of cations
Formation of Cations
  • The electron configuration of the sodium ion is the same as that of a neon atom.
slide16
To draw a Lewis Dot Structure for an ion

1. Draw the structure for the neutral atom.

Example for Cl-

2. Add or subtract electrons depending on the ions charge. add an electron for each negative charge

subtract an electron for each positive charge

3. Place your structure in [brackets] and label the charge.

slide17
Classwork-

Draw dot structures for the following ions

18. H- 19. H+ 20. Na+ 21. Be2+

22. Al3+ 23. Li+ 24. Ca2+ 25. O2-

26. F- 10. S2- 27. Cl- 28. I-

29. As3-

30. Why don’t noble gases form ions?

slide18
A magnesium atom attains the electron configuration of neon by losing both valence electrons. The loss of valence electrons produces a magnesium cation with a charge of 2+.
slide19
Walnuts are a good dietary source of magnesium. Magnesium ions (Mg2+) aid in digestive processes.
slide20
Cations of Group 1A elements always have a charge of 1+.
  • Cations of group 2A elements always have a charge of 2+.
slide21
The gain of negatively charged electrons by a neutral nonmetal produces an anion.
    • The name of an anion typically ends in -ide.
slide23
A gain of one electron gives chlorine an octet and converts a chlorine atom into a chloride ion. It has the same electron configuration as the noble gas argon.
slide24
Both a chloride ion and the argon atom have an octet of electrons in their highest occupied energy levels.
slide25
In this equation, each dot in the electron dot structure represents an electron in the valence shell in the electron configuration diagram.
slide27
The ions that are produced when atoms of chlorine and other halogens gain electrons are called halide ions.
    • All halogen atoms have seven valence electrons.
    • Halogen atoms gain one electron to achieve the electron configuration of a noble gas (a stable full octet). Ex. Cl-
7 1 section quiz
7.1 Section Quiz.
  • 1. How many valence electrons are there in an atom of oxygen?
    • 2
    • 4
    • 6
    • 8
7 1 section quiz1
7.1 Section Quiz.
  • 2. Atoms that tend to gain a noble gas configuration by losing valence electrons are
    • metals.
    • nonmetals.
    • noble gases.
    • representative elements.
7 1 section quiz2
7.1 Section Quiz.
  • 3. When a magnesium atom forms a cation, it does so by
    • losing two electrons.
    • gaining two electrons.
    • losing one electron.
    • gaining one electron.
7 1 section quiz3
7.1 Section Quiz.
  • 4. When a bromine atom forms an anion, it does so by
    • losing two electrons.
    • gaining two electrons.
    • losing one electron.
    • gaining one electron
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