integrated physics and chem
posted by Anonymous
Element A and element B have bonded and formed compound AB. Which of the following statements is true?
A. Compound AB has chemical and physical properties that are completely different from those of A and B.
B. Compound AB has chemical and physical properties that are a blend of the properties of A and B.
C. Compound AB has chemical and physical properties that are similar to A but not like B.
D. Compound AB has chemical and physical properties that are similar to B but not like A.
Just thinking of NaCl, I'd have to go with A.
There is one more common type of bond—the metallic bond. This type of bond, true to its name, occurs between atoms of metals. It is responsible for giving metals many of their physical properties, especially their ability to conduct electricity. Most metals are similar to sodium and calcium as discussed above; that is, they have one or two electrons in their valence shells. The periodic table entries of two metals you are probably more familiar with (iron and copper) bear out this generalization:
For a metallic solid to gain the stability of the octet, the atoms must move close enough to each other that their valence shells overlap. However, the electrons are not transferred from one atom to the neighboring atom; nor are they shared between adjoining atoms. Rather, the valence electrons form a "sea of electrons" surrounding the positive fixed ions. The electrons are free to roam from ion to ion. These moving electrons enable metals to conduct electricity. The strong attraction of the positive nuclei for the "sea of electrons" allows metals to be pounded into shapes (malleable) and pulled into wires (ductile) without breaking the bonds. A metallic bond can be illustrated as shown below. Each positive ion represents the placement of the nuclei of a metal nucleus that has lost its valence electrons. It does not move. The electrons, though, are free to move.