Ion An atom or group of atoms that

A positive ion an atom or group of atoms that has lost one or more electrons. 

Ions are derived from electrically neutral atoms (or groups of atoms) but differ from them in that they possess an electrical charge. This charge is positive for the hydrogen ion and for ions derived from metals (or nonmetallic groups such as NH4) and negative for ions derived from nonmetals or acidic radicals. 

The atom, ion, or group of a molecular entity that approaches and forms a covalent or coordinate covalent bond with the substrate during a reaction. Any attacking nucleophile is an entering group. 

The relative fragility of the connections between the constitutive atoms of the molecule is an intrinsic properly of the structure. Tliis strength of connection is conditioned by the properties of the constitutive atoms. The breaking of the intramolecular chemical connections enables the release of atoms, ions, or groups of atoms that have the ability to exchange with other molecular entities. 

But let us go back to our considerations of environmentally relevant nucleophiles. Because of its great abundance, water plays a pivotal role among the nucleophiles present in the environment. A reaction in which a water molecule (or hydroxide ion) substitutes for another atom or group of atoms present in an organic molecule is commonly called a hydrolysis reaction. We note that in a hydrolysis reaction, the... 

It is, of course, impossible to measure the absolute size of an isolated atom its electron cloud extends to infinity. It is possible to calculate the radius within which (say) 95% of its total electron cloud is confined but most measures of atomic/ionic size are based upon experimental measurements of internuclear distances in molecules and crystals. This means that the measurement is dependent on the nature of the bonding in the species concerned, and is a property of the atom or ion under scrutiny in a particular substance or group of substances. This must always be borne in mind in making use of tabulated radii of atoms or ions. The most important dictum to remember is that radii are significant only insofar as they reproduce experimental internuclear distances when added together. The absolute significance of a radius is highly suspect,... 

An ion is an atom or group of atoms with a net electrical charge. Anions are negatively charged ions that are formed by addition of electrons. Cations are positively charged ions that are formed by the loss of electrons. 

Ion An atom or a group of bonded atoms that carries an electrical charge. 

In the following year, 1905, Werner published his great book on coordination chemistry, and this had a powerful influence on Lewis. Werner proposed that in coordination compounds, atoms or groups of atoms surrounded a central atom to form an electrically charged ion or a neutral compound, and the geometrical or structural theory seemed to fit very nicely with Lewis s ideas. All that was needed (and it was a big all ) was a clearer picture of the electrical nature of atoms. 

Some groups or families are given special names and have certain properties that should be addressed. But first you must understand why elements are put into the same group. Think about a family you know, not a chemical family, but a human family. Children look like their parents. They learn to do things from their parents and do them in the same way. The same holds true for the elements in the families of the periodic table they react the same way (for the most part). As you learned in the last chapter, each element has a certain number of valence electrons. As you will learn in the next chapter, it is the number of valence electrons of an atom that determines its chemical reactivity. Because the elements in a family have the same number of valence electrons, they will have a similar chemical reactivity. For example, Na and K can be compared in electron configuration and ions formed ... 

An ion is an atom (or group of atoms) that has lost or gained one or more electrons through oxidation or reduction. 

Ion an atom or a group of atoms that has a net positive or negative charge. (2.7)... 

The chlorine molecule undergoes homolysis (Sec. 1.14) that is, cleavage of the chlorine -chlorine bond takes place in a symmetrical way, so that each atom retains one electron of the pair that formed the covalent bond. This odd electron is not paired as are all the other electrons of the chlorine atom that is, it does not have a partner of opposite spin (Sec. 1.6). An atom or group of atoms possessing an odd (unpaired) electron is called a free radical. In writing the symbol for a free radical, we generally include a dot to represent the odd electron just as we include a plus or minus sign in the symbol of an ion. 

The adjective simple describes an ion formed from a single atom. A simple ion could also be called monatomic, which means one-atom. Just as the prefix mon- means one, the prefix poly- means many. The term polyatomic ion means a charged group of two or more bonded atoms that can be considered a single ion. A polyatomic ion as a whole forms ionic bonds in the same way that simple ions do. 

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