POLAR COVALENT BONDS RESULT FROM AN UNEVEN SHARING OF ELECTRONS

Once you have become proficient at building these models, test your expertise by building models for difluoromethane, CH2F2 ethane, 

C2H6 hydrogen peroxide, H202 and acetylene, C2H2. Keep in mind that each carbon atom must have four covalent bonds, each oxygen must have two, and each fluorine and hydrogen must have only one. 

No fair peeking at the Hands-On Chemistry Insights at the end of this chapter until you have made an honest attempt to build these molecules. 

If the two atoms in a covalent bond are identical, their nuclei have the same positive charge, and therefore the electrons are shared evenly. We can represent these electrons as being centrally located by using an electron-dot structure in which the electrons are situated exactly halfway between the two atomic symbols. Alternatively, we can draw a probability cloud (see Section 5-5) in which the positions of the two bonding electrons over time are shown as a series of dots. Where the dots are most concentrated is where the electrons have the greatest probability of being located  

In a covalent bond between nonidentical atoms, the nuclear charges are different, and consequently the bonding electrons may be shared unevenly. This occurs in a hydrogen—fluorine bond, where electrons are more attracted to fluorine s greater nuclear charge  

The bonding electrons spend more time around the fluorine atom. I or this reason, the fluorine side of the bond is slightly ne tivc and, becau.se the bonding electrons have been drawn away from the hydrt en atom, the hydrogen side of the bond is slightly positive. This separation of charge is called a dipole (pronounced die-pole ) and is represented either by the characters 5— and 8+, read 

When the two atoms in a covalent bond have the same electronegativity, no dipole is formed (as is the ca.se with H ,) and the bond is cla.ssificd as a nonpolar bond. When the electronegativities of the atoms differ, a dipole may form (as with HF) and the bond is cla.s.sifled as a polar bond. Just how polar a bond is depends on the difference between the electronegativity values of the two atoms—the greater the difference, the more polar the bond. 

List these bonds in order of increasing polarity P-F, S-F, Ga-F, Ce-F (F, fluorine, atomic number 9 P, phosphorus, atomic number 15 S, sulfur, atomic number 16 Ga, gallium, atomic number 31 Ge, germanium, atomic number 32)  

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Polar Covalent Bonds Result from an Uneven Sharing of Electrons... 

POLAR COVALENT BONDS RESULT FROM AN UNEVEN SHARING OF ELECTRONS... 

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