Biology Forums - Study Force

Last I took Biology was during high school years. Now I'm getting old so may be some of you students can help me out with this for my school project. Would to get some more insight of the two types of bonds. May be a quick summarize so I can understand this a little better rather than reading the chapter from the book.  :-\

Welcome to the forum rb40gte.

An ionic bond is a type of chemical bond (electrostatic) that involves a metal and a nonmetal ion.

For instance: Sodium (Na+) [the metal] and chlorine (Cl-) [the non-metal]. When you put these two together, you get a salt.

The following compounds are formed by ionic bonds: sodium chloride, calcium fluoride, and calcium chloride since they involve a metal and non-metal.

A covalent bond is a bond formed by the sharing of a pair of electrons by two atoms. An example of a covalent bond is H2. Hydrogen alone has one electron, but to form a stable bond, it requires two electrons. It gets this other electron from another hydrogen atom by sharing it. Another example of covalent bonding is the oxygen (O2)-hydrogen bonds in water. Oxygen has 6 electrons around a single oxygen atom. It shares 1 of its six electrons with hydrogen atom and another of its six electrons with another hydrogen atom. This way the hydrogen ions are happy (both have a pairs of electrons) and the oxygen atom is also happy since it has 8 electrons surrounding it (the ideal stable state).

Another cool example of a covalent bond is sand (silicon dioxide). Interestingly, covalent bonds are found in the sugar-phosphate backbones, which are the same throughout DNA molecules. Also, ionic bonds are typically weaker than covalent bonds; for instance, most salts readily dissolve in water into sodium ions and chlorine ions, but if you were to put a protein in water (recall that proteins are held nostly by covalent bonds) it would hold itself together quite nicely.

Bio_man  8)

Here is an activity to help you understand further:

Covalent Bond Activity:

http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/bo/m1/s2/index.htm (http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/bo/m1/s2/index.htm)

Ionic Bond Activity:

http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/bo/m1/s1/index.htm (http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/bo/m1/s1/index.htm)

An ionic bond is a bond in which electrons are not shared but rather transferred between atoms, so an atom donates an electron and becomes positively charged and another atom receives the electron and becomes negatively charged. This happens because atoms seek stability ( having full orbitals ) and they achieve that either by losing electrons or winning electrons. The atom that now has a positive charge and the one having a negative charge are attracted to each other and stay close due to the electrostatic force between them, this is why we say that they have a bond between them, but they don't necessary have to stay close to each other to remain stable, this is why an ionic bond is not a strong one.

On the other hand, a covalent bond is a bond in which neither atoms donate or receive electrons, they share their electrons, so both become stable but only while their electrons are being shared, so breaking up the bond would cause them to go to a less stable state, which is why this bond is hard to be broken, so it is a stronger bond.

It is good to add that most covalent bonds aren't 100% covalent and have some ionic character since atoms in a covalent bond have different electonegativity, so one can pull electrons towards it stronger than the other, so electrons in this case are not completely shared but are pulled closer to an atom and farther from the other one, so a partial negative charge is formed on the atom pulling the electrons more towards it ( the more electronegative one ) and a partial positive charge is created on the less electronegative atom.