Magnesium and chlorine have valence electrons in their highest energy level. Magnesium forms Mg2+ ions by losing two valence electrons to attain the electron configuration of neon. Chlorine forms Cl- ions by gaining one electron to attain the electron configuration of argon. Ions are formed by atoms gaining or losing electrons to achieve a noble gas configuration.

1. Bellwork- valence electrons
Write the electron configurations
for magnesium and chlorine.
How many electrons do these
elements have in their highest
energy level?

2. Lecture 7.1- Ions

3. Valence electrons are the
electrons in the highest occupied
energy level of an atom.

4. 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.

5. The group number tells you
the number of valence
electrons.
Group 6A = Group 16
= 6 valence electrons

6. Valence Electrons
Applications of Group 4A Elements
Carbon Silicon Germanium

7. Lewis Dot Diagrams
• Because valence electrons are so important
to the behavior of an atom, it is useful to
represent them with symbols.

8. A Lewis dot diagram illustrates
valence electrons as dots (or other
small symbols) around the chemical
symbol of an element.

9. • Each dot represents one valence
electron.

10. • Each dot represents one valence
electron.
• The element’s symbol represents
the core of the atom—the nucleus
plus all the inner electrons.

11. 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

12. 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.

13. 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.

14. Metals lose their valence electrons,
leaving a complete octet in the
next-lowest energy level.
Non-metals gain electrons to
achieve a complete octet.

15. Metals produce cations
when they lose electrons.

16. 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.

17. Formation of Cations
The electron configuration of the
sodium ion is the same as that of a
neon atom.

18. Formation of Cations
The electron configuration of the
sodium ion is the same as that of a
neon atom.

19. Formation of Cations
The electron configuration of the
sodium ion is the same as that of a
neon atom.

20. Formation of Cations
The electron configuration of the
sodium ion is the same as that of a
neon atom.

21. Using electron dot structures, you can
show the ionization more simply.

22. To draw a Lewis Dot Structure for an ion
1. Draw the structure for the neutral atom.
Example for Cl-

23. 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

24. 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.

25. 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?

26. 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+.

27. Walnuts are a
good dietary
source of
magnesium.
Magnesium ions
(Mg2+) aid in
digestive
processes.

28. Cations of Group
1A elements
always have a
charge of 1+.
Cations of group
2A elements
always have a
charge of 2+.

29. The gain of negatively charged
electrons by a neutral
nonmetal produces an anion.

30. The gain of negatively charged
electrons by a neutral
nonmetal produces an anion.
•The name of an anion
typically ends in -ide.

31. The figure shows the
symbols of anions
formed by some
elements in Groups
5A, 6A, and 7A.

32. 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.

33. Both a chloride ion and the argon atom
have an octet of electrons in their
highest occupied energy levels.

34. Both a chloride ion and the argon atom
have an octet of electrons in their
highest occupied energy levels.

35. Both a chloride ion and the argon atom
have an octet of electrons in their
highest occupied energy levels.

36. Both a chloride ion and the argon atom
have an octet of electrons in their
highest occupied energy levels.

37. Both a chloride ion and the argon atom
have an octet of electrons in their
highest occupied energy levels.

38. In this equation, each dot in the
electron dot structure represents an
electron in the valence shell in the
electron configuration diagram.

39. The negatively
charged ions in
seawater—the
anions—are mostly
chloride ions.

40. The ions that are produced when atoms of
chlorine and other halogens gain electrons
are called halide ions.

41. 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.

42. 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 a stable full octet.
Ex. Cl-

43. Oxygen is in Group 6A.

44. Oxygen is in Group 6A.

45. Oxygen is in Group 6A.

46. Oxygen is in Group 6A.

47. Oxygen is in Group 6A.

48. Oxygen is in Group 6A.

50. 7.1 Section Quiz.
1. How many valence electrons are there in an
atom of oxygen?
a. 2
b. 4
c. 6
d. 8

51. 7.1 Section Quiz.
1. How many valence electrons are there in an
atom of oxygen?
a. 2
b. 4
c. 6
d. 8

52. 7.1 Section Quiz.
2. Atoms that tend to gain a noble gas
configuration by losing valence electrons are
a. metals.
b. nonmetals.
c. noble gases.
d. representative elements.

53. 7.1 Section Quiz.
2. Atoms that tend to gain a noble gas
configuration by losing valence electrons are
a. metals.
b. nonmetals.
c. noble gases.
d. representative elements.

54. 7.1 Section Quiz.
3. When a magnesium atom forms a cation, it
does so by
a. losing two electrons.
b. gaining two electrons.
c. losing one electron.
d. gaining one electron.

55. 7.1 Section Quiz.
3. When a magnesium atom forms a cation, it
does so by
a. losing two electrons.
b. gaining two electrons.
c. losing one electron.
d. gaining one electron.

56. 7.1 Section Quiz.
4. When a bromine atom forms an anion, it does
so by
a. losing two electrons.
b. gaining two electrons.
c. losing one electron.
d. gaining one electron

57. 7.1 Section Quiz.
4. When a bromine atom forms an anion, it does
so by
a. losing two electrons.
b. gaining two electrons.
c. losing one electron.
d. gaining one electron