METALS AND COMPOUNDS

METALS AND COMPOUNDS

Non-Metals and Their Compounds
A nonmetal or non-metal in chemistry is a chemical element which does not have the characteristics of a metal. There is no exact and thorough definition of nonmetals. They exhibit more variability in their characteristics than metals.

Some physical properties of nonmetals are:

• They have the tendency to be extremely volatile. This means that they can easily turn into vapor.

• Their elasticity is very low

• They are excellent insulators of heat and electricity

• They mainly exist as monatomic gases, with some of them possessing more considerable although, still open-packed diatomic or polyatomic forms, contrary to metals which are almost all solid and tightly-packed.

• When a non-metal is a solid, it is characteristically possesses a sub metallic property, it has a dull appearance and is brittle, contrary to metals, which are lustrous, ductile or malleable.

• Non-metals normally have lower densities than metals.

• They are poor conductors of heat and electricity when compared to metals.

• They have significantly lower melting points and boiling points than those of metals apart from carbon

Some chemical properties of non-metals are:

• They have lofty ionization energy and electro negativity values

• They accept or share electrons when reacted with other elements or compounds.

The elements that are normally classified as nonmetals are 17 in number. They are mostly gases like hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon. One of them is liquid Bromine is the liquid non-metal.

Some of them are solids. Solid no-metals are carbon, phosphorus, sulfur, selenium, and iodine.

As you move across the period of a typical periodic table, nonmetals adopt structures that have increasingly fewer close neighbors. Polyatomic nonmetals have arrangements or shapes with either 3 close neighbors. This is exemplified in carbon when nit is in its standard stated in graphite. They can as well possess 2 close neighbors as you would obtain in sulphur. On the centrally, diatomic non-metals like hydrogen, possess only one close neighbor, and the monatomic noble gases, like helium do not have any close neighbor.

The systematic decline in the number of close neighbors is connected with a decrease in metallic character and a boost in nonmetallic character. The difference that exists among the three types of nonmetals, with regards to declining metallic properties is not unlimited. Boundary overlaps arise as remote elements in every category illustrate or start to exhibit less-distinct, hybrid related or a distinctive property.

Even though the numbers of elements that metals five times exceed the numbers of elements that are nonmetals, two of the nonmetals—hydrogen and helium—constitute above 99 per cent of the visible Universe, and another one, oxygen, constitute almost half of the Earth's crust, oceans and atmosphere. Living organisms are as well made entirely of nonmetals. Nonmetals constitute countless more compounds than metals.

Chemically, the nonmetals have comparatively high ionization energy and high electro negativity.

They usually exist as anions or oxyanions in aqueous solution.

They generally form ionic or interstitial compounds when reacted with metals, as opposed to metals which form alloys. Non metal have acidic oxides while the regular oxides of the metals are basic in nature.

Non- metallic elements
The elements that are usually categorized as nonmetals consist of one element in group 1 and group 14: hydrogen (H) and carbon (C); 2 elements in group 15 pnictogens ie nitrogen (N) and phosphorus (P); 3 elements in group 16 (the chalcogens): oxygen (O), sulfur (S) and selenium (Se); most elements in group 17 known as the halogens: fluorine (F), chlorine (Cl), bromine (Br) and iodine (I); and all elements in group 18 known as the noble gases, with the likely exclusion of ununoctium (Uuo).

The difference between nonmetals and metals is not very clear. The outcome is that some intermediate elements which are deficient of a predominance of either nonmetallic or metallic properties are classified as metalloids; and some elements under the category of nonmetals are as an alternative occasionally classified as metalloids, or vice versa. For instance, selenium (Se), a nonmetal, is occasionally classified alternatively as a metalloid, mainly in environmental chemistry; and astatine (At), which is a metalloid and a halogen, is occasionally alternatively classified as a nonmetal.

Nonmetals have structures in which every atom normally forms (8 − N) bonds with (8 − N) closest neighbors, where N stands for the number of valence electrons. Every one of the atom is by this means capable of filling its valence shell and attaining a stable noble gas configuration. The exclusions to the (8 − N) rule take place with hydrogen which merely requires one bond to achieve its octet configuration, carbon, nitrogen and oxygen. Atoms of the last three elements are adequately minute that they are capable of forming substitute and more stable bonding structures, with smaller amount of close neighbors.

Thus, carbon is capable of forming its layered graphite structure, and nitrogen and oxygen are capable of forming diatomic molecules with triple and double bonds, in that order. The bigger size of the rest non-noble nonmetals deteriorates their ability to form multiple bonds and they on the contrary form two or more single bonds to two or more dissimilar atoms. Sulfur, for instance, forms an eight-membered molecule in which the atoms are prearranged in a circle, with ever one of the atoms forming two single bonds to dissimilar atoms.

From left to right across the periodic table, as metallic character declines, nonmetals consequently assume structures that illustrate a steady decline in the numbers of closest neighbors—three or two for the polyatomic nonmetals, all the way through one for the diatomic nonmetals, to zero for the monatomic noble gases.

A comparable prototype takes place usually, at the level of the whole periodic table, in comparing metals and nonmetals. There is a switch from metallic bonding among the metals on the left hand side of the table through to covalent or Van der Waals (electrostatic) bonding among the nonmetals on the right side of the periodic table. Metallic bonding have the tendency to engage close-packed central symmetric structures with a high number of close neighbors. Other metals and metalloids, between the true metals and the nonmetals, have the tendency to posses more complex structures with an intermediary number of close neighbors.

Nonmetallic bonding, at the right side of the periodic table, exhibits open-packed directional or muddled up structures with fewer or zero close neighbors. As noted, this fixed reduction in the number of close neighbors, as metallic character declines and nonmetallic character augments, is reflected in the midst of the nonmetals, which have structures that gradually vary from polyatomic, to diatomic, to monatomic.

This happens with key categories of metals, metalloids and nonmetals, there are a little variation and overlapping of properties within and across every category of nonmetal. Amongst the polyatomic nonmetals, carbon, phosphorus and selenium which are at the margin of the metalloids start to show some metallic character.

Polyatomic nonmetals
Four nonmetals are well-known to form polyatomic bonding in their average states, in either distinct or extensive molecular forms: carbon (C, in the form of graphite sheets; phosphorus in the form of P4 molecules; sulfur in the form of S8 molecules; and selenium Se, in the form of helical chains. Polyatomic nonmetals exhibits more metallic character than the adjoining diatomic nonmetals; every one of them are solid, mainly semi-lustrous semiconductors with electro negativity values that are midway to more or less high. Sulfur is the least metallic of all the polyatomic nonmetals due to its properties of dull appearance, brittle comportment, and stumpy conductivity. This is a characteristic found in all sulfur allotropes. It nonetheless exhibits a number of metallic characters, either essentially or in its compounds with other nonmetals.

The differences between the polyatomic nonmetals and the diatomic nonmetals are: They possess higher organization numbers, elevated melting points, and high boiling points. They have a wider liquid ranges and lower room temperature instability. In general, they exhibits a marked tendency to occur in allotropic forms, and a stronger tendency to catenate; and have a weaker propensity to form hydrogen bonds.

Diatomic nonmetals
There are7 nonmetals that are diatomic molecules in their standard states. These are hydrogen (H2); nitrogen (N2); oxygen (O2); fluorine (F2); chlorine (Cl2); bromine (Br2); and iodine (I2). They are usually greatly insulating, exceedingly electronegative, non-reflective gases, but bromine which is a liquid, and iodine which is a solid, are both unstable at room temperature.

The diatomic nonmetals can be differentiated from the polyatomic nonmetals because they have lower coordination numbers, lesser melting points and lesser boiling points; and possessing narrower liquid ranges and larger room temperature explosive nature.

Noble gases
Six nonmetals exist in nature as monatomic noble gases: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn). They are composed of chemical elements with extremely similar properties. In their standard states, they are all colorless, odourless, nonflammable gases with typically extremely low chemical reactivity.

Elemental gases
Hydrogen, nitrogen, oxygen, fluorine, chlorine, in addition to the noble gases is jointly referred to as the elemental gases. They are differentiated by having the lowest densities, they have lowest melting and boiling points, strongest insulating properties, and highest electronegativity plus ionization energy values in the periodic table.

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