Which of these chemical elements is represented on the atomic table by a single letter?
Elements are the basic building blocks of all matter, and they vary widely in their abundance. Each element is represented by a one or two letter symbol, which is an internationally-used abbreviation based either on its English name or Latin name. The letter or letters are followed by the element’s atomic number, which is a unique integer based on the number of protons in an atom’s nucleus.
Originally, the elements were arranged by Dmitri Mendeleev in a table according to their increasing atomic mass. At this time, there was no understanding of the internal structure of an atom, so the arrangement was mostly a guide to its properties. Once the inner workings of an atom were understood, it was found that many of its properties are determined by the way that it’s outer electrons are arranged. For example, an oxygen atom in water has 2 electrons in its 1s orbital and 4 electrons in its 2p orbitals (see Figure 3-23.1). This is called sp3 hybridization.
In the modern periodic table, elements that have similar physical and chemical properties are grouped together in columns, which are sometimes called periods. Periods range from one row with just two elements to six or more rows with 18 or more elements each. In some cases, elements are also grouped into families, which have similar chemical properties but differ in other ways, such as how they react with other elements.
