Gold leaf is gold that has been hammered into extremely thin sheets by goldbeating and is often used for gilding. Gold leaf is available in a wide variety of karats and shades. 22-karat yellow gold is the most commonly used.
Gold leaf is sometimes confused with metal leaf but they are different products. The term metal leaf is normally used for thin sheets of metal of any color that do not contain any real gold. 24 karats is pure gold. Real yellow gold leaf is about 91% pure gold. Silver colored white gold is approximately 50% pure gold.
The periodic table is a tabular arrangement of the chemical elements, organized on the basis of their atomic numbers, electron configurations, and recurring chemical properties. Elements are presented in order of increasing atomic number (the number of protons in the nucleus). The standard form of the table consists of a grid of elements laid out in 18 columns and 7 rows, with a double row of elements below that. The table can also be deconstructed into four rectangular blocks: the s-block to the left, the p-block to the right, the d-block in the middle, and the f-block below that.
The rows of the table are called periods; the columns are called groups, with some of these having names such as halogens or noble gases. Since, by definition, a periodic table incorporates recurring trends, any such table can be used to derive relationships between the properties of the elements and predict the properties of new, yet to be discovered or synthesized, elements. As a result, a periodic table—whether in the standard form or some other variant—provides a useful framework for analyzing chemical behavior, and such tables are widely used in chemistry and other sciences.