Monatomic ions defined

Oxidation numbers (also called oxidation states) are used as a sort of bookkeeping method for keeping track of the electrons in polyatomic ions or compounds that have covalent bonds. (For monatomic ions, the charge on the ions works just as well.) Oxidation number is defined as the number of electrons in a free atom minus the number controlled by that atom in the compound. The control of electrons in a covalent bond is assigned to the more electronegative atom of the bond. Eight simple rules can be used to determine the oxidation number of an element from the formula of its compound or ion (Section 16.1). 

Define the term isoelcctronic. When comparing sizes of monatomic ions of elements in the same period of the pe-... 

We define the oxidation states (or oxidation numbers) of the atoms in a covalent compound as the imaginary charges the atoms would have if the shared electrons were divided equally between identical atoms bonded to each other or, for different atoms, were all assigned to the atom in each bond that has the greater attraction for electrons. Of course, for ionic compounds containing monatomic ions, the oxidation states of the ions are equal to the ion charges. 

Ions, defined as particles that carry electrical charges, exist in condensed phases (solids and liquids) as electrically neutral combinations of cations and anions electrolytes. The ions may be bound or relatively free to migrate. Ions may be monatomic, such as K+or Cr, they may consist of a few atoms, such as ammonium, NH4+, or sulfate, S04 , or even considerably more than a few, such as nitrobenzoate, 02NC6H4C02, or tetrapropylammonium, (C3H7)4N+. They may even consist of very many atoms and may carry many dispersed charges and are then referred to as poly-ions, constituting the dissociated part of polyelectrolytes. Some biological moieties, such as polypeptides, proteins, and nucleic acids, as well as suitable synthetic molecules are examples of polyelectrolytes. 

A monatomic ion, like an atom, is a nucleus surrounded by a distribution of electrons. The ionic radius is a measure of the size of the spherical region around the nucleus of an ion within which the electrons are most likely to be found. As for an atomic radius, defining an ionic radius is somewhat arbitrary, because an electron distribution never abruptly ends. However, if we imagine ions to be spheres of definite size, we can obtain their radii from known distances between nnclei in crystals. (These distances can be determined accurately by observing how crystals diffract X rays.) ... 

COAL 1 Define and distinguish between cations and anions. COAL 2 Identify the monatomic ions that are isoelectronic with a given noble-gas atom and write the electron configuration of those ions. 

This chapter should be read in conjunction with Chapter 6, Coronas, Plasmas, and Arcs. A plasma is defined as a gaseous phase containing neutral molecules, ions, and electrons. The numbers of ions and electrons are usually almost equal. In a plasma torch, the plasma is normally formed in a monatomic gas such as argon flowing between two concentric quartz tubes (Figure 14.1). 

The enthalpies of formation of aqueous ions may be estimated in the manner described, but they are all dependent on the assumption of the reference zero that the enthalpy of formation of the hydrated proton is zero. In order to study the effects of the interactions between water and ions, it is helpful to estimate values for the enthalpies of hydration of individual ions, and to compare the results with ionic radii and ionic charges. The standard molar enthalpy of hydration of an ion is defined as the enthalpy change occurring when one mole of the gaseous ion at 100 kPa (1 bar) pressure is hydrated and forms a standard 1 mol dm-3 aqueous solution, i.e. the enthalpy changes for the reactions Mr + (g) — M + (aq) for cations, X (g) — Xr-(aq) for monatomic anions, and XOj (g) —< XO (aq) for oxoanions. M represents an atom of an electropositive element, e.g. Cs or Ca, and X represents an atom of an electronegative element, e.g. Cl or S. 

In addition to the statistical mechanical temperatures, a distribution temperature, called the ionization temperature, and defined by the Saha equation, is frequently referred to (D2, S3). In its simplest form—for a monatomic gas—the Saha equation states that the equilibrium established between the species present [positive ions (+), electrons (e), and neutral atoms (0) ] is a function of temperature,... 

As mentioned earlier, the sizes of isolated ions are ill-defined, but in condensed phases, the ions can be assigned definite sizes, because of the strong repulsion of the contagious electronic shells. In crystals, the interionic distances can be measured by x-ray and neutron diffraction with an uncertainty of a fraction of a pm and individual ionic radii (at least for monatomic and globular ions) have been assigned. These radii, r, do depend on the coordination numbers of the ions and a set for the characteristic coordination in salt crystals that are usually met have been estabhshed by Shannon and Prewitt [43,44],... 

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