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Calculating the Relative Molecular Mass (RMM) of Compounds The Relative Molecular Mass of a compound is the sum of the masses of all the atoms present in the molecule. It is often shortened to RMM. The RMM is used in many sorts of calculations in chemistry, and so you must be able to calculate it to answer all the other calculations you might meet. This is not particularly difficult, as long as you can do simple arithmatic and know the relative atomic masses of the elements, sometimes called the RAM of an element. The following examples show you how to do this. If you already know how to do these calculations, move on to the  RMM Tests page  for some practice. But if you are a bit unsure, here are some examples for you. We will use the relative atomic masses given below. It might help if you have some paper and a pen handy, and use a calculator. Relative Atomic Masses Element Symbol RAM       Carbon C 12 Hydrogen H 1 Oxygen O 16 Sodium Na 23 Sulphur S 32 Chlorin...

In  physics  and  chemistry ,  ionization energy  ( IE ) ( American English  spelling),  ionisation energy  ( British English  spelling) is the minimum energy required to remove the most loosely bound  electron  of an isolated gaseous  atom ,  positive ion , or  molecule . [1]  The first ionization energy is quantitatively expressed as Ionization energy trends plotted against the  atomic number , in units  eV . The ionization energy gradually increases from the  alkali metals  to the  noble gases . The maximum ionization energy also decreases from the first to the last row in a given column, due to the increasing distance of the valence electron shell from the nucleus. Predicted values are used for elements beyond 104. X(g) + energy ⟶ X + (g) + e − where X is any atom or molecule, X +  is the resultant ion when the original atom was stripped of a single electron, and e −  is the...

For the values of the ionization energies of the elements, see  Molar ionization energies of the elements  and  Ionization energies of the elements  In  physics  and  chemistry ,  ionization energy  ( IE ) ( American English  spelling),  ionisation energy  ( British English  spelling) is the minimum energy required to remove the most loosely bound  electron  of an isolated gaseous  atom ,  positive ion , or  molecule . [1]  The first ionization energy is quantitatively expressed as Ionization energy trends plotted against the  atomic number , in units  eV . The ionization energy gradually increases from the  alkali metals  to the  noble gases . The maximum ionization energy also decreases from the first to the last row in a given column, due to the increasing distance of the valence electron shell from the nucleus. Predicted values are used for elements beyond 104. X(g...

Electronegativity , symbolized as  χ , is the tendency for an  atom  of a given  chemical element  to attract shared  electrons  (or  electron density ) when forming a  chemical bond . [1]  An atom's electronegativity is affected by both its  atomic number  and the distance at which its  valence electrons  reside from the charged nucleus. The higher the associated electronegativity, the more an atom or a substituent group attracts electrons. Electronegativity serves as a simple way to quantitatively estimate the  bond energy , and the sign and magnitude of a bond's  chemical polarity , which characterizes a bond along the continuous scale from  covalent  to  ionic bonding . The loosely defined term  electropositivity  is the opposite of electronegativity: it characterizes an element's tendency to donate valence electrons. Electrostatic potential map of a water molecule, where the oxy...

This article is about the table used in chemistry and physics. For other uses, see  Periodic table (disambiguation) . The  periodic table , also known as the  periodic table of the  ( chemical )  elements , is a tabular display of the  chemical elements . It is widely used in  chemistry ,  physics , and other sciences, and is generally seen as an icon of chemistry. It is a graphic formulation of the periodic law, which states that the properties of the chemical elements exhibit a  periodic  dependence on their  atomic numbers . The table is divided into four roughly rectangular areas called  blocks . The rows of the table are called  periods , and the columns are called  groups . Elements from the same column group of the periodic table show similar chemical characteristics.  Trends  run through the periodic table, with  nonmetallic  character (keeping their own electrons) increasing from left to r...

Periodic trends  are changes in the properties of  chemical elements  along the  periodic table  of elements. Major periodic trends include  electronegativity ,  ionization energy ,  electron affinity ,  atomic radius ,  ionic radius ,  metallic character , and  chemical reactivity . The periodic trends in properties of elements These trends reflect the changes in atomic properties along the  periods  (horizontal rows) and  groups  (vertical columns) in the periodic table. They give a qualitative assessment of the properties of each element. However, not all properties strictly follow these trends, for example, the  ionization energies  in group 3, the  electron affinities  in group 17 or the  densities  in group 1 elements ( alkali metals ). History

Skip to Main content Radioactive Element Radioactive elements are in an unstable, high-energy state and emit radiation to return to a stable, low-energy state. From:  Clinical Ophthalmic Oncology, 2007 Related terms: Ionization Protein Radioisotope Neoplasm DNA Uranium Radium View all Topics Pollution, Soil Thomas E. McKone, in  Encyclopedia of Toxicology (Second Edition) , 2005 Transformation The transformation of toxic substances in soil can have a profound effect on their potential for human exposure and accumulation by biota. Transformation processes in soil include physical processes such as radioactive decay; chemical processes such as photolysis, hydrolysis, and oxidation/reduction; and biological processes such as microbial transformations. All of these processes can significantly reduce the concentration of a substance or alter its structure in such a way as to enhance or diminish its toxicity. Radioactive Decay Radioactive elements  are made up of atom...