Overview
Some chemical elements use ionic bonds to form compounds. Those compounds use electrical attraction between elements to maintain chemical bonds, and rules govern which elements gain or lose electrons. Table salt, or sodium chloride (NaCl), is an example of an ionic compound.
How Are Ionic Compounds Formed?
Ionic compounds are formed from positively charged ions (cations) and negatively charged ions (anions). In the case of sodium chloride, sodium is positively charged and chlorine is negatively charged. They bond in a specific crystal pattern, in which the positively charged sodium gives up its extra electron to bond with chlorine. Ionic compounds conduct electricity when they are dissolved in water, because the ions that separate are electrically charged. The solid compounds themselves are electrically neutral.
Do Only Single Elements Form Ions?
Many elements form ions that exist as only that type of element, and they enter into reactions and bonding with other elements. However, some compounds are also ionic and can join with others in ionic bonds. The compound ammonium (NH4) is a positive ion of +1, while the compounds hydroxide (OH) and nitrate (NO3) are negative ions of -1. Sulfates (SO4) and carbonates (CO3) are negative ions of -2, and phosphates (PO4) are negative ions of -3.
Which Elements Form Ions?
Since elements are arranged in the periodic table according to their atomic weight, they are indirectly arranged according to the number of electrons in their outermost shells. Therefore, the noble gases such as helium, neon, argon, krypton, and xenon are the least reactive of all the elements, as they already have full outer shells. Elements such as lithium, sodium, and potassium have only one electron in their outermost shells, while elements such as fluorine, chlorine, bromine, and iodine have seven electrons in their outermost shells.
What Is the Octet Rule?
The most stable configuration of electrons is a full valence, usually eight for most levels and types of atoms. A compound such as sodium chloride is stable because the one electron in the outermost shell of the sodium atom can combine with the seven electrons in the outermost shell of the chlorine atom to form a stable configuration of eight electrons. Some elements form ions that have more than one positive charge, and they combine with those elements that form ions that have the same value of negative charge. For example, the compound magnesium oxide contains magnesium ions, that have a value of +2, and oxygen ions, that have a value of -2.
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