difference is too large (metals and nonmetals) an ionic bond will form with the metal giving its electron to the nonmetal. 3. What is the difference b...
Chapter 12: Review Worksheet Answers 1. What circumstance must exist for a bond to be purely covalent? How does a polar covalent bond differ from an ionic bond? A bond is purely covalent when there is no difference in the electronegativities of the atoms involved in the bond. Therefore, diatomic elements have purely covalent bonds. A polar covalent bond occurs when elements of differing electronegativities bond, creating a dipole moment. The electrons are still shared, but the more electronegative atom has a larger “portion”. 2. How does the polarity of a bond depend on the difference in electronegativities of the two atoms participating in the bond? If two atoms have exactly the same electronegativity, what type of bond will exist between the atoms? If two atoms have vastly different electronegativity, what type of bond will exist between them? See question 2. A slight difference in electronegativity will lead to a slightly polar covalent bond. A very large difference in electronegativity will lead to a very polar covalent bond; if the difference is too large (metals and nonmetals) an ionic bond will form with the metal giving its electron to the nonmetal. 3. What is the difference between a polar bond and a polar molecule (one that has a dipole moment)? A polar bond is covalent but electrons are more attracted to the atom with the higher electronegativity. A polar molecule has positive and negative regions due to the molecule’s shape as well as the polarity of the bonds. 4. When atoms of a metal react with atoms of a nonmetal, what type of electron configuration do the resulting ions attain? Explain how the atoms in a covalently bonded compound can attain noble gas electron configurations. Metals and nonmetals react to form ionic compounds, with the metal donating its electron to the nonmetal and the atoms being held together by electrostatic attraction (a very strong bond). Atoms in covalent compounds achieve noble gas configuration by sharing valence electrons so that both atoms have eight electrons. 5. On the basis of their electron configurations, predict the formula of the simple binary ionic compound likely to form when the following pairs of elements react with each other. a. barium and chloride BaCl2: [Xe]6s2 + [Ne]3s23p5 Require 2 Cl to accept 2 e-s from Ba b. sodium and fluorine NaF: [Ne]3s1 + [He]2s22p5 1 Cl accepts 1 e- from Na c. potassium and oxygen K2O [Ar]4s1 + [He] 2s22p6 Require 2 K’s to give 2 e – to O 6. Why is a cation always smaller and an anion always larger than the respective parent atom? A cation is always smaller because it has lost electrons to drop down an energy level (smaller electron cloud). An anion is always larger because it gains electrons to fill an energy level (larger electron cloud). 7. Write the electron configuration for each of the following atoms and for the simple ion that the element most commonly forms. In each case, indicate which noble gas has the same electron configuration as the ion. a. Nitrogen 1s22s22p3 ion: 1s22s22p6 (gain 3e to be like Ne, N3-) b. Selenium 1s22s22p63s23p64s23d104p4 (gain 2e to be like Kr, Se2-) c. Aluminum 1s22s22p63s23p1(lose 3e to be like Ne, Al3+)
