Non-Metal

The elements of group 17 – halogens and group 18 – noble gases are also non-metals, but they are described in separated chapters. Hydrogen, nitrogen and oxygen are gases at standard conditions, and carbon, phosphorus, sulfur and selenium are solids. Hydrogen is placed in group 1 of the periodic table, carbon in group 14, nitrogen and phosphorus in group 15, and oxygen, sulfur and selenium in group 16. These non-metals are the most important chemical elements in the Universe, because they form the stars, the biochemistry and the life itself. Composed of a single proton and a single electron, hydrogen (H) is the simplest and the most abundant element in the Universe. It is estimated that 90% of the visible Universe is composed of hydrogen. Hydrogen is the raw fuel that stars burn in nuclear reactions to produce energy. The estimated crustal abundance is 1.40x103 mg/kg, thus, the estimated abundance in the ocean is 1.08x105 mg/lit. Hydrogen has three common isotopes: protium, deuterium and tritium. Carbon (C) is one of the most abundant chemical elements in the Universe and basic block regarding to form life. Carbon is most commonly obtained coal deposits. Three naturally occurring allotropes of carbon are known to exist: amorphous, graphite and diamond. The estimated crustal abundance is 2.00x102 mg/kg, and the estimated oceanic abundance is 2.80x101 mg/lit. The number of stable isotopes is 2. Nitrogen (N) is the fifth most abundant element in the Universe and makes up about 78% of the Earth's atmosphere. The estimated crustal abundance is 1.90x101 mg/kg, and the estimated oceanic abundance is 5.00x10-1 mg/lit. It has 2 stable isotopes. Today, phosphorus is primarily obtained from phosphate rock Ca3(PO4)2. Phosphorus has three main allotropes: white, red and black. The estimated crustal abundance is 1.05x103 mg/kg, thus, the estimated abundance in the ocean is 6.00x10-2 mg/lit. There is 1 stable isotope. Oxygen is the third most abundant element in the Universe and makes up nearly 21% of the Earth's atmosphere. Oxygen (O) accounts for nearly half of the mass of the Earth's crust, two thirds of the human body and nine tenths of the mass of water. The estimated crustal abundance is 4.61x105 mg/kg, and the estimated oceanic abundance is 8.57x105 mg/lit. There are 3 stable isotopes. Sulfur (S) is a component of many common minerals, such as galena (PbS), gypsum (Ca(SO4)2 x 2H2O), pyrite (FeS2), etc. It displays in three allotropic forms: orthorhombic, monoclinic and amorphous. The estimated crustal abundance is 3.50x102 mg/kg, and the estimated oceanic abundance is 9.05x102 mg/lit. There are 4 stable isotopes. Selenium (Se) occurs in minerals such as eucairite (CuAgSe), crooksite (CuThSe) and clausthalite (PbSe). The estimated crustal abundance is 5.00x10-2 mg/kg, and it has 6 stable isotopes.    

Elements that tend to gain electrons to form anions during chemical reactions are called non-metal. These are electronegative elements with high ionization energies. They are non-lustrous, brittle and poor conductors of heat and electricity (except graphite, allotropic modification of carbon. At room temperature hydrogen, nitrogen and oxygen are diatomic gases, H2, N2 and O2, respectively. Carbon, phosphorus, sulfur and selenium are in solid state of matter at room temperature. Non-metals are very brittle and cannot be roll into wires and pounded into sheets. The solid non-metals have a subatomic appearance and are not generally ductile and malleable. They usually have lower densities than metals and tend to have significantly lower melting and boiling points than those of metals.

Chemically the non-metals mostly have high ionization energies, high electron affinities and high electronegativity. In general, the higher an element's ionization energy, electron affinity and electronegativity, the more non-metallic that element is. Non-metals, when reacting with metals, tend to gain electrons (typically attaining noble gas electronic configuration) and become anions. The atoms of metals and non-metals make ionic bonds between each other, otherwise the atoms of non-metals make covalent bonds. They are relatively strong oxidizing agents, especially oxygen. Oxygen reacts with metals to form metallic oxides which with water form hydroxides. Furthermore, it reacts with non-metals to form non-metallic oxides which with water form acids.

The non-metals react more with metals than with-non metals. Usually, non-metals react with other non-metals in high temperature and do not react with water.

These elements and their compounds are crucial for life exiting on Earth. Water (H2O) is the universal solvent, and the unique properties of water molecule enable the life on Earth. All biochemical reactions in living cells happen in water solutions. The Earth's atmosphere contains nitrogen and oxygen, and oxygen is important for breathing of aerobic organisms. Nitrogen is the building block of the biomolecules such as amino-acids, proteins and DNA. The most important is carbon which is the part of lipids, carbohydrates, amino-acids, DNA, RNA and many other biomolecules. We can say that the life on Earth is based on carbon chemistry.

There are nearly ten million known carbon compounds and an entire branch of chemistry, known as organic chemistry is devoted to their study. Some of the most common carbon compounds are: carbon dioxide (CO2), carbon monoxide (CO), carbon disulfide (CS2), chloroform (CHCl3), methane (CH4), acetylene (C2H2), etc. Oxygen is also highly reactive element and capable of combining with most other elements. Due to the oxygen can be found in many minerals and ores as well as for rocket fuel production. Nitrogen gas is largely inert and is used as a protective shield in the semiconductor industry and during certain types of welding. Liquid nitrogen is an inexpensive cryogenic liquid used for refrigeration and preservation of biological samples. Nitrogen and phosphorus compounds are used in fertilizer production. Phosphoric acid (H3PO4) is used in soft drinks and to create many phosphor compounds. Sulfur is used in the manufacture of sulfuric acid (H2SO4).

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