![]() Similar ideas about these four elements existed in other ancient traditions, such as Indian philosophy.Ī few extra elements were known in the age of alchemy: zinc, arsenic, antimony, and bismuth. The four roots, which the Athenian philosopher Plato called elements, were earth, water, air and fire. Around 330 BCE, the Greek philosopher Aristotle proposed that everything is made up of a mixture of one or more roots, an idea originally suggested by the Sicilian philosopher Empedocles. Each ion has a single charge, one positive and one negative, so we need only one ion of each to balance the overall charge.Nine chemical elements – carbon, sulfur, iron, copper, silver, tin, gold, mercury, and lead, have been known since before antiquity, as they are found in their native form and are relatively simple to mine with primitive tools. ![]() It is conventional to use the lowest ratio of ions that are needed to balance the charges.įor example, consider the ionic compound between Na + and Cl −. Because the charges on the ions are characteristic, sometimes we have to have more than one of a cation or an anion to balance the overall positive and negative charges. The key to writing proper ionic formulas is simple: the total positive charge must balance the total negative charge. ![]() A Ca 2+ cation has twice as much charge as a Cl - anion, so it will be able to attract and cancel out the charge on two Cl - anions. Two ions with opposite charges will be attracted to each other as being close to one another allows them to cancel out the additional charge they are carrying. Two ions with the same charge will push away from each other. Ions behave the same way on the atomic scale. ![]() When the magnets push away from each other we're trying to force two like charges together. One side of each of our magnets is positive and one side of each of our magnets is negative. If you've ever tried to force two refrigerator magnets together you'll remember that there was one side of each magnet that clicked together and there was one side of each magnet that pushed against the other. A proper ionic formula has a cation and an anion in it an ionic compound is never formed between two cations only or two anions only. An element symbol without a charge written next to it is assumed to be the uncharged atom.Ĭhemical formulas for ionic compounds are called ionic formulas. If the charge is a single positive or negative one, the number 1 is not written if the magnitude of the charge is greater than 1, then the number is written before the + or − sign. The magnitude of the charge is listed as a right superscript next to the symbol of the element. Note the convention for indicating an ion. Unfortunately, there is little understanding which two charges a metal atom may take, so it is best to just memorize the possible charges a particular element can have. Cobalt (Co) is another element that can form more than one possible charged ion (2+ and 3+), while lead (Pb) can form 2+ or 4+ cations. For example, iron (Fe) atoms can form 2+ cations or 3+ cations. A few elements, all metals, can form more than one possible charge. Examination of the table in the link given shows that there are some exceptions to the previous point. A more complete table of ions and their charges can be found at Monotomic Ions of Various Charges. \) is helpful in determining the charge on a large number of our cations and anions it's hardly complete.
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