IONS, ELECTRIC FORCES, AND THE FORMATION OF COMPOUNDS

In chemistry, more than 107 known elements react with one another to form compounds.  A compound is a substance that is formed when two or more elements combine chemically and has properties different from each of the individual component elements.  A compound cannot be separated simply because the elements are chemically bonded together.  Water (H₂O), a compound, is used to put fires out.  However, Hydrogen, an element, and Oxygen, an element, are explosive in element form.  Thus, we emphasize again that compounds' properties are likely to be very different from the properties of the elements with which they are formed.

Compounds are formed by combining elements and utilizing electrons from those elements.  There are essentially two things that elements can do with electrons when they combine.  Elements can share electrons or transfer them to another element.  A compound formed by sharing electrons is called a covalent compound, while a compound formed by transferring electrons is an ionic compound.  The electrons that are transferred or shared are those on the outside of the atom and are called Valence electrons.

All elements seek to have eight electrons in the outside level or transfer them to empty the last level.  It would be easier for this element to transfer the two electrons it has rather than find six more.  This element will transfer two electrons, but an element with seven electrons would find it easier to gain one to equal eight electrons than transfer seven.  Both of these examples are ionic compounds.  When an element gains or loses electrons, it moves from being neutral to having a charge because the number of protons and electrons is no longer equal.  An element with a charge is called an ion.  If an element loses two electrons, it now has two more protons than electrons, and that element would have a charge plus 2 (+2).  A positive ion is called a cation.  An element that gains two electrons would now have two more electrons than protons, and this element would have a charge of negative 2 (-2).  A negative ion is called an anion.  

An element with four electrons in its outer shell is in a unique position since it is precisely in the middle of 0 and 8.  The element would rather not lose or attract four electrons but instead share electrons.  A compound formed by sharing electrons is a covalent compound.  The force that holds compounds together is electrical.  The center of an atom is positively charged, and the outside is negatively charged.  Opposite particles attract, so the negative on one part of the atom attracts the positive on the other.  These attractions are very short-range forces, but the strength of these bonds is responsible for many chemical properties.  Some of the properties include boiling point, melting point, and vaporization point, and the stronger the bond, the higher these points will be.