Homework: Atomic Structure II

1. Define a cation. How does an atom become a cation?
2. Under what circumstances does an atom become a cation? Why would it do so?
3. Define an anion. How does an atom become an anion?
4. Under what circumstances does an atom become an anion? Why would it do so?
5. Define a covalent bond.
6. How does the formation of a covalent bond help an atom to fill its valence shell?
7. Fill in the blanks in the following table, paying special attention to atomic charge.

   Name	Symbol	No. of p+	No. of n0	No. of e–	Overall Charge
   iron-54	5426Fe2+
   		5	6	5
   			16	18	–3
   		79	118	78
   barium-137			81		+2

8. One isotope of a metallic element has mass number 65 and 35 neutrons in its nucleus. The cation derived from the isotope has 28 electrons. Write the symbol for this cation.
9. One isotope of an alkali metal has mass number 87 and 50 neutrons in its nucleus. The cation derived from the isotope has 36 electrons. Write the symbol for this cation.
10. One isotope of a non-metallic element has mass number 81 and 46 neutrons in its nucleus. The anion derived from the isotope has 36 electrons. Write the symbol for this anion.
11. What is a Group in the periodic table? What do you know about the valence electrons of the elements in a group?

12. The elements in a group have similar chemical and physical properties. Remember the video you watched in class about how the alkali metals (Li, Na, K, Rb, and Cs) react when exposed to water. Using what you know about the valence electrons of elements in a group explain why elements in a group have similar properties.
13. What is another name for an electron shell? (Look back at the text of the group activity or at your notes).
14. What is the reason electrons only exist in shells and never between them? Think about quantum energy.
15. Why do atoms try to have filled shells?
16. What is the difference in terms of chemical reactivity between an atom with an unfilled valence shell and one will a filled valence shell?
17. Based on your knowledge of groups in the periodic table, predict the likely charges of the following atoms if they were to form ions by gaining or losing electrons to fill their valence shell:
    

    Ca                        Li                        Cl                       N                          Ne                        Mg                        Si
    
    Ba                        Rb                        I                        As                        Xe                        Sr                        Pb
    
    

    
    Show the charge of each atom by writing it as a superscript next to the symbol. Underneath each symbol write how many e^- are gained or lost.
18. Draw the Lewis electron dot structure of the atoms from the previous problem.
19. Draw a pictures of an atom using a solar system model (draw a model of Ar). In the model of the atom include the nucleus and each shell showing all electrons in each shell. Next to it draw a model of the solar system showing all the planets (include Pluto if you want to). Leave space to list at least four similarties and four differences between the two models.

20. Describe an everyday situation in which potential energy is minimized. Several examples were given in class and several were given in the group activity handout.
21. How is the situation you described above like the way atoms work when they try to have full valence shells?
22. Define the following key terms:
    1. energy level
    2. filled shell
    3. valence shell
    4. covalent bond
    5. minimize energy
    6. overall charge