Answer the following questions. CHEMISTRY BONDING REVIEW 1. What are the three kinds of bonds which can form between atoms? The three types of Bonds are Covalent, Ionic and Metallic. Name Date Block 2. What kind of bond normally forms between the following: a) Two identical atoms? A Pure or Non-polar Covalent Bond b) A metal and a nonmetal? An Ionic Bond 3. What is meant by a polar covalent bond? It is a bond where electrons are not shared equally between elements. The electro-negativity greater is less than 0.4 4. Which of these forms an ionic bond? a) CO b) CaBr 2 This is the closest to an ionic bond. c) HBr d) Cl 2 5. Arrange the following atoms based on electronegativity. Put the most electronegative atom on the right and the least electronegative atom on the left. P Al Cl Mg Mg Al P Cl 6. Which bond is the most polar? Which bond is the least polar? a) P-Cl b) H-H This one is the least polar c) N-H d) C-F This one is the most polar 7. When two nitrogen atoms combine to form a nitrogen molecule, how many electrons are shared to give each atom a complete octet? The P obitals - P x, P y and P z Three (3) electrons from each atom (total 6 electrons or 3 pairs of electrons).
8. How many electrons do each of the atoms below need to gain, lose, or share to achieve noble gas electron configuration? a) S Needs to gain 2 electrons b) Mg Needs to lose 2 electrons c) C Needs to share, lose or gain 4 electrons 9. In which of the atom/ion pairs is the ion smaller than the atom? a) S/S -2 b) Ca/Ca +2 Ca +2 is the smallest c) Li/Li + Li + a is smaller d) I/I - 10. Draw Lewis structures for these ionic compounds. a) MgCl 2 Cl Mg Cl b) Na 2 O 11. Draw Lewis structures for the molecules or ions below. a) H 2 S b) HCCH H C C H c) PO 4-3 d) HI
12. Draw Lewis structures for the molecules or ions below, provide the number of bonded pair of electrons, the number of un-bonded pair of electrons and the molecular shape. a) PCl 3 Bonded Lone Total Shape 3 1 4 Trigonal pyramidal b) H 2 O 2 2 4 Bent (angular) c) BF 3 3 0 3 Trigonal Planar d) MgBr 2 2 0 2 Linear e) SiH 4 4 0 4 Tetrahedral 13. What is ionization energy? Write a general equation representing it. It is the energy required to remove electrons from gaseous atoms or ions. Example of equation is Li + --> Li + 1e - 14. Discuss what is meant by the term multiple ionization energy. What happens to ionization energy as these electrons are removed? It is the ability to remove more than one electron from an atom. Ionization increases as electrons are removed. 15. What is meant by the term electron affinity? Write a general equation representing it. It is defined as the amount of energy released when an electron is added to a neutral atom or molecule to form a negative ion 16. Describe the shielding effect and how it affects ionization energy and electron affinity. Electrons form shells around an atomic nucleus. The inner electrons shells shield the outer electrons shells and reduce the affect of the nuclear "pull" on those outer electrons. The shielding provided by the inner electrons means it will take less energy to free outer electrons from their orbitals, and thus the ionization energy of an outer electron is reduced by the effects of shielding.
17. Make a chart showing periodic trends for ionization energy, electron affinity, electro-negativity, and atomic size, include their relationship to metals and nonmetals. Check notes and handouts for Periodic Trend Table. 18. Fluorine has the highest electro-negativity, what does that tell you about the element fluorine? It strongly attracts an electron. 19. How does a metal ion size compare to its original atom? How does a nonmetallic ion compare to its original nonmetal? Metals are smaller than the original atom. (They lose electrons.) Non-metals are larger than the original atom. (They gain electrons.) 20. Distinguish between a polar and non-polar bond, and a polar and non-polar molecule. Use examples in your discussion. Polarity is measured on a scale of electro-negativity (the electron disparity between two elements that are combined in a compound). The more electrons you take from your partner element in the bonding process, the greater your negative charge, and the greater your electro-negativity. There are three terms to describe the polarity of a given molecular bond: Ionic, Polar covalent, and Non-polar covalent. Ionic is the most polar - essentially, one atom physically takes electrons from another atom, creating a huge electron disparity between the two atoms. This tends to happen in molecules where one atom has very few valence electrons and the other has a lot of valence electrons. Sodium chloride (NaCl) is a good example of an ionic bond. Polar covalent is the mid-range - technically closer to ionic. This happens when one atom attempts to take electrons from its partner, but cannot quite attract them all to itself. The result is a covalent bond between the two atoms where the valence electrons are "shared," but the sharing is unequal. One atom pulls the "shared" electrons a little closer to itself. Polar covalent bonds usually occur between very electronegative elements; hydrogen paired with elements like oxygen and fluorine almost always creates polar covalent bonds. A good example of a polar covalent bond is found in water (H 2 O). Non-polar covalent is the least polar - in fact, it is not polar at all. This occurs when valence electrons are shared equally between two atoms. There is little or no tendency for either atom to pull any of the electrons toward itself. Non-polar covalent bonds can often be seen in molecules with two non-metals. Methane (CH 4 ) is an example of a non-polar covalent bond
21. Distinguish between ionic, covalent and metallic compounds, include differences in bonding electrons and properties. Make a chart and include examples. Ionic vs Covalent Compounds The difference between ionic and covalent compounds can be confusing. A basic definition of an ionic compound is that they are molecules that consist of charged ions. These ions have opposite (both negative and positive) charges. On the other hand, covalent compounds are non-metals which are bound together, and consist of two electrons that are shared between two atoms. The molecules of an ionic compound are bonded together by the electrical attraction of the two or more ions. These ions can be of two types cation and anion. Cation refers to the ions with a positive charge, while anion refers to the ions with a negative charge. Cations are usually metals, while anions are usually non-metals, or polyatomic. On the other hand, a covalent compound is usually formed when two non-metals are bonded together. In this type of compound, the electrons are shared (and not transferred), and this causes the bond between them. Ionic compounds have a high melting and boiling point, whereas covalent compounds have a comparatively lower melting and boiling point. The reason for this fact, is that ionic compounds require a huge amount of energy to break their ionic bonds, and pull apart the positive and negative charges. Covalent compounds are separated much more easily, because they are formed from distinct molecules that do not interact with each other. The bonds of the ionic compounds are more crystal-like than the bonds of the covalent compound. Therefore, covalent compounds are softer, and more flexible. Covalent compounds are also more flammable than ionic compounds, due to the fact that they often contain Carbon and Hydrogen. Ionic compounds help to conduct electricity in water, as they are charge carriers. Covalent compounds do not have this capability, because they do not contain ions. Ionic compounds are also more soluble in water than covalent compounds. This is because water dissolves polar substances, which is the consistency of the ionic compound, whereas covalent compounds are non-polar. Summary: 1. Ionic compounds are formed by the transfer of electrons that are positively and negatively charged, whereas, covalent compounds are formed by sharing the electrons. 2. The melting and boiling points of ionic compounds are much higher compared to those of the covalent compounds. 3. Ionic compounds are hard and crystal-like, while covalent compounds are softer and more flexible. 4. Covalent compounds are more flammable when compared to ionic compounds.
22. Distinguish between shared and unshared electron pairs. A shared pair of electrons, they are two electrons in a covalent bond that alternate between atoms; one electron from one atom and one electron from the other atom. Unshared pairs are two electrons that are not involved in a bond and have already filled their shells. In a dot diagram there would be two electrons paired together on one side of an atom, but not shown to be part of the bond. 23. Which of the following statements explains why ionic compounds generally conduct an electrical current? A. The shared electrons of the molecular bonds become free to move when the compound is dissolved in water. **B. When ionic compounds dissolve in water, their ions dissociate and become free to move through the solution and conduct electricity. C. When an ionic compound dissolves in water, the compound remains intact but takes on a negative charge that allows it to flow through the solution and conduct electricity. D. Dipole moments form hydrogen bonds in solution and allow electrical current to flow.