1.1 What is Chemistry?

8.1. Ions http://www.ck12.org

nearest noble gas (8 valence electrons, except for helium, which has 2).

• Electron dot diagrams are used to help us visualize the arrangement of valence electrons in a given chemical
  species.


• When an element loses one or more electrons, a cation is formed. Metals typically become cations when they
  interact with other chemical species.


• Some transition metals can produce ions with multiple different charges due to the optional participation of d
  electrons.


• When an element gains one or more electrons, an anion is formed. Nonmetals typically become anions when
  they interact with other chemical species.

Lesson Review Questions

1. Draw electron dot diagrams for one metal and one nonmetal.


2. Predict whether each of the following is more likely to become a cation or an anion.
   (a) Ca
   (b) Na
   (c) F
   (d) Br
   (e) S


3. Write the ground state electron configurations for the following elements, and predict the ion that will form
   when each atom becomes isoelectronic with the nearest noble gas.
   (a) Be
   (b) Mg
   (c) O
   (d) Al


4. Describe the change that is happening when Li→Li+.


5. What would be the electron configuration for Mg−? Use the octet rule to explain why this is not likely to be a
   very stable ion.


6. What would be the electron configuration for F+? Use the octet rule to explain why this is not likely to be a
   very stable ion.


7. Element X has a total of 16 electrons.
   (a) Write the electron configuration for element X.
   (b) How many electrons away from a complete octet is this element?
   (c) Make a prediction about the ion that this element might form in an ionic compound.


8. Element Z has a total of 12 electrons.
   (a) Write the electron configuration for element Z.
   (b) How many electrons away from a complete octet is this element?
   (c) Make a prediction about the ion that this element might form in an ionic compound.


9. Write the ground state configuration for the following elements. Then, show how the element ionizes to
   become isoelectronic with the nearest noble gas. Example: Mg [1s^2 2s^2 2p^6 3s^2 ]

Mg

[Ne] 2 s^2

→Mg^2 +

[Ne]

+2e−

(a) Na

(b) Ca

(c) N