![]() ![]() In other words, even though an element group might break a trend, the elements within the group display periodic properties. periodic table, Organized array of all the chemical elements in approximately increasing order of their atomic weight. Elements with similar properties are arranged in the same column (. However, the behavior of the noble gases is periodic. A table in which the chemical elements are arranged in order of increasing atomic number. The noble gases are an exception to the trend since these elements have filled electron valence shells and electron affinity values approaching zero. Nonmetals usually have higher electron affinities than metals. Electron affinity increases moving across a period and decreases moving down a group. Electron Affinity - This is a measure of readily an atom accepts an electron.Not all elements form stable negative ions in which case the electron affinity is zero or even positive. So the more negative the electron affinity the more favourable the electron addition process is. Atom and ion sizes shrink moving across a period because the increasing positive charge of the nucleus pulls in the electron shell. The electron affinity is the potential energy change of the atom when an electron is added to a neutral gaseous atom to form a negative ion. Although it might seem like increasing the number of protons and electrons in an atom would always increase its size, the atom size doesn't increase until a new electron shell is added. Ionic radius is the distance for ions of the atoms and follows the same trend. Atomic radius decreases moving left to right across a period and increases moving down a group. An anion is relatively larger in size than its parent atom. The atomic size of a cation will be smaller than that of the parent atom. The Ionic radius can be described as the distance between the nucleus of an ion and the outermost shell of the ion. Transition Metals: Groups 3-12 - d and f block metals have 2 valence electrons. The periodic table is one of the most basic and fundamental concepts in chemistry. Alkaline Earth Metals: Group 2 (IIA) - 2 valence electrons. Atomic Radius - This is half the distance between the middle of two atoms just touching each other. When an atom loses an electron it forms a cation and when it gains an electron it becomes an anion. Another common method of categorization recognizes nine element families: Alkali Metals: Group 1 (IA) - 1 valence electron.Electronegativity - A measure of how readily an atom forms a chemical bond. Electronegativity increases moving left to right across a period and decrease moving down a group.Ionization energy increases moving left to right across the table and decreases moving down a group. Ionization Energy - This is the energy needed to completely remove an electron from an atom or ion.
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