MSE 150.02HOMEWORK 2: SOLUTIONS
 
Chapter 2
2.19    Compare and contrast the three primary bonds in detail (draw a schematics for each). Explain what the driving force is formation of such bonds or in other words why do atoms want to bond at all?
AnswerIonic Bonds – metals and nonmetals bond through electron transfer and ionic bonding. Ionic bonding is typically observed between atoms with large differences in their electronegativities; for instance atoms of group 1A or 2A(reactive metals) with atoms of group 6,4. or 7 A (reactive nonmetals). In short, one atom loses an electron and forms a cation, another atom gains the electron lost by the first atom and forms an anion. After the electron transfer process is completed, both atoms will have completed their outer electronic structure and take on the structure of a noble gas. The electrostatic attraction forces between the two ions will then hold the ions together to form an ionic bond.Covalent Bonds – is typically observed between atoms with small differences in their electronegativities and mostly between non-metals. At first, the nucleus of one atom attracts the electron cloud of the other; the atoms get closer to each other. As they get close, the two electron clouds interact and both atoms start to take ownership of both electrons (share electrons). The atoms keep getting closer until they reach the equilibrium point in which the two atoms will form a bond by sharing their electrons, both completing their outer electronic structure, and reaching the lowest state of energy.Metallic Bonds – during solidification, from a molten state, the atoms of a metal pack tightly together, in an organized and repeating manner. All the atoms contribute their valence electrons to a “sea of electrons” or the “electron charge cloud”. These valence electrons (free electrons) are delocalized, move freely in the sea of electrons, and do not belong to any specific atom. The nuclei and the remaining core electrons of…