0.6 Bonding 07

Lab 5: bonding 07

Objective

• To test various compounds and determine their conductivity and bonding.
• To understand how electronegativity can predict bond type.
• To learn the relationship between bonding and conductivity.

Grading

• Pre-Lab (10%)
• Lab Report Form (80%)
• TA Points (10%)

Background information

A chemical bond is a link between atoms that results from the mutual attraction of their nuclei for electrons. Bonding occurs in order to lower the total potential energy of each atom or ion. Throughout nature, changes that decrease potential energy are favored.

 The main types of bonds that we will be covering are ionic bonds, covalent bonds, and metallic bonds. An ionic bond is the chemical bond that results from the electrostatic attraction between positive (cations) and negative (anions) ions. The ionic relationship is a“give and take”relationship. One ion donates or“gives”electrons, while the other ion receives or“takes”electrons.

A covalent bond is a chemical bond resulting from the sharing of electrons between two atoms. There are two main types of covalent bonds. The first being non-polar covalent bonds. These are bonds in which the bonding electrons are shared equally by the united atoms-with a balanced electrical charge. Polar covalent bonds are covalent bonds in which the united atoms have an unequal attraction for the shared electrons.

The role of electrons in bonding has been well-studied. The ability of an atom or element to attract electrons to itself is known as the element’s electronegativity. A scale was first calculated by the Nobel laureate Linus Pauling and is commonly called the Pauling electronegativity scale. The actual electronegativity values aren’t as important as how they compare to a different element. In Part I of today’s experiment, you will compare electronegativity values to predict the type of bond that will exist between two elements.

In the solution state, ionic compounds dissociate to give a separation of charge. The separation of charge allows for the flow of electrons through solution. The flow of electrons is classified as conductivity. A strong electrolyte is a compound that when dissolved in water will completely ionize or dissociate into ions. That is, the compound exists in water only as individual ions, and there are no intact molecules at all. This solution conducts electricity well. A weak electrolyte is a compound that when dissolved in water only partially ionizes or dissociates into ions. That is, the compound exists in water as a mixture of individual ions and intact molecules. This solution conducts electricity weakly. A nonelectrolyte is a compound that when dissolved in water does not ionize or dissociate into ions at all. In water, this compound exists entirely as intact molecules. The solution does not conduct electricity at all. By measuring the conductivity of a dissolved compound, we can classify it as a nonelectrolyte, weak electrolyte, or strong electrolyte and determine its ability to dissociate into ions. There are four common compounds that you will encounter in today’s lab.