Sodium atomic properties

The alkali metals have the interesting property of dissolving in some non-aqueous solvents, notably liquid ammonia, to give clear coloured solutions which are excellent reducing agents and are often used as such in organic chemistry. Sodium (for example) forms an intensely blue solution in liquid ammonia and here the outer (3s) electron of each sodium atom is believed to become associated with the solvent ammonia in some way, i.e. the system is Na (solvent) + e" (sohem). 

The Group 1 elements are soft, low-melting metals which crystallize with bee lattices. All are silvery-white except caesium which is golden yellow "- in fact, caesium is one of only three metallic elements which are intensely coloured, the other two being copper and gold (see also pp. 112, 1177, 1232). Lithium is harder than sodium but softer than lead. Atomic properties are summarized in Table 4.1 and general physical properties are in Table 4.2. Further physical properties of the alkali metals, together with a review of the chemical properties and industrial applications of the metals in the molten state are in ref. 11. 

There is convincing experimental evidence for the following important statement. To a degree of approximation satisfactory for most analytical work, the mass absorption coefficient of an element is independent of chemical or physical state. This means, for example, that an atom of bromine has the same chance of absorbing an x-ray quantum incident upon it in bromine vapor, completely or partially dissociated in potassium bromide or sodium bromate in liquid or solid bromine. X-ray absorption is predominantly an atomic property. This simplicity is without parallel in absorptiometry. 

The phase Na2Sx is sodium polysulfide, a material with a sulfur content of between 3 and 5. The anode reaction takes place at the liquid sodium - (3"-alununa interface. Here sodium atoms lose an electron and the Na+ ions formed enter the conduction planes in the electrolyte. The cathode reaction, which occurs at the interface between the (3"-alumina and the liquid sulfur forms sodium polysulfides. Despite the desirable properties of the cell, technical and economic considerations have acted so as to curtail large-scale commercial production. 

Adsorption of third particles other than water molecules on metal electrodes influences the microstructure and the electrochemical activity of the electrode interface. For example, the interface of metal electrodes usually acts as a Lewis add in the adsorption of water molecules, but its Lewis add-base property is altered by the adsorption of third partides. Electronegative particles such as oi en molecules, if adsorbed, increase the local Lewis acidity of interfacial metal atoms around the adsorption sites whereas, electropositive particles such as sodium atoms, if adsorbed, increase the local Lewis basicity around their adsorption sites. Furthermore, the adsorption energy of water molecules is altered by the coadsorption of third partides on metal electrodes. 

Electrons in a solid or a liquid may be separated into two groups the core electrons which are the inner, tightly bound electrons with properties sometimes known by studying isolated atom or molecule, and the valence electrons which are the outer, relatively loosely bound electrons. The valence electrons are highly sensitive to the state of aggregation of the system. For our present discussion we might consider as valence electrons the outer 3s electron detached from a sodium atom in liquid ammonia, or the excess electron in a liquid rare gas. 

The elementary substance sodium is at ordinary temperatures a soft, white metal. It consists of sodium atoms arranged in a regular structure (Fig. 4-5) similar to that described for copper, but not identical with it. The elementary substance chlorine is a greenish-yellow gas, consisting of diatomic molecules, Gig. Sodium metal will burn in chlorine gas, to give a new substance, which is sodium chloride (com mon salt), with properties greatly different from those of either of the two substances from which it is made. The sodium atoms in the sodium metal which reacted and the chlorine atoms in the chlorine gas which reacted are present in the sodium chloride formed by the reaction, but rearranged and ordered in a new way. 

Chemists call this salt sodium chloride. Sodium chloride is made from sodium cations and chloride anions. As illustrated in Figure 7, these ions have very different properties than those of their parent atoms. That is why salt is not as dangerous to have around your house as the elements that make it up. It does not react with water like sodium metal does because salt contains stable sodium ions, not reactive sodium atoms. 

Now you can relate the submicroscopic models of the formation of NaCl, H2O, and CO2 to their macroscopic properties mentioned in Section 4.1. When elements combine, they form either ions or molecules. No other possibilities exist. The particles change dramatically, whether they change from sodium atoms to sodium ions or hydrogen and oxygen atoms to water molecules. This change explains why compounds have different properties from the elements that make them up. 

Sodium, atomic number 11, begins the third period and has a single 3s electron beyond the configuration of neon. Sodirun s electron configuration is ls 2s 2p 3s. If you compare this with the electron configuration of lithium, ls 2s, it s easy to see why sodium and lithirun have similar chemical properties. Each has a single electron in the valence level. 

Like certain combinations of metallic elements which show degrees of mutual solubility, so organic polymer blocks show varying tendencies to "alloy" in the solid state. The synthesis and properties of block polymers is a developing science which leads to important materials and engineering applications.(65) In this section we describe the preparation of a BAB block terpolymer of f-methylstyrene and styrene.(66) Sodium atoms are used to initiate polymerization in liquid tetrahydrofuran solutions of monomer cooled... 

If one has differentiated information about elementary particles like protons, neutrons and electrons which connect to questions of chemical bonding, misconceptions can arise which mix bent water molecules or the 11-protons nucleus of a sodium atom with macroscopic characteristics of matter (see also Sect. 4.3). Since electrons are not ordinary basic particles of matter in the sense of atoms, ions and molecules, but are recognized more as charged clouds, orbital or through the particle-wave duality, the mixing of macroscopic and sub-microscopic characteristic properties should be avoided more carefully. 

When an atom loses or gains electrons, it forms a monatomic ion, an ion from a single atom. (All the ions described in this section are monatomic ions.) The chemical properties of an ion are not at all like those of the atom from which it came the electrical charge becomes the dominant property. A sodium atom, Na, and a sodium ion, Na+, are chemically very different. Sodium atoms could never exist in contact with water, for example, because they react vigorously with water, but sodium ions exist in water without a problem. 

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