Non Metals: Properties, Importance, Disadvantages

Non metals are elements on the periodic table's right side. Non-metals are either gases or solids; the only exception is Bromine which is a liquid. Non-metals are not as lustrous as metals and have a dull colour; the only exception is Iodine which is lustrous. You can't hammer or mould a non-metal; if you hit it, it would shatter. Sulphur is one such example, and if you hit it with a hammer, it breaks. Whereas Diamond, an allotrope of Carbon, is the hardest known substance even if it is a non-metal. Diamond is known to have the highest melting and boiling point.

Read More: Equations of Motion by Graphical Method

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Non Metallic Elements 

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Various non-metal elements have been explained below:

Noble Gases (Helium and Neon)

They are seen in the rightmost column of traditional periodic tables. Because of their generally low chemical reactivity, they are referred to as noble gases. They are all colourless, odourless, and nonflammable, and they have extremely comparable qualities. 

Noble gases have weak interatomic forces of attraction due to their closed valence shells, resulting in extremely low melting and boiling temperatures. That is why, under typical conditions, they are all gases, even those with atomic weights more significant than many typically solid elements.

Halogens (Fluorine and Chlorine)

While nonmetal halogens are caustic and highly reactive, they can be found in seemingly harmless substances like table salt NaCl. Their tremendous chemical activity as nonmetals contrasts with the alkali metals, such as sodium and potassium, which are found at the far left of the periodic table and have a similarly excellent chemical activity. 

Fluorine and chlorine are pale yellow and yellowish-green gases, respectively, with bromine being a reddish-brown liquid and iodine being a silvery metallic solid. The first three are insulators electrically, but iodine is a semiconductor.

Metalloids Elements (Silicon and Boron)

They occupy a diagonal section in the p-block on the periodic table, stretching from Boron in the upper left to tellurium in the lower right. They run parallel to the dividing line between metals and nonmetals seen in the periodic tables. They're brittle, and they're only good at conducting electricity and heat. 

Semiconductors include Boron, silicon, germanium, and tellurium. Arsenic and antimony have semimetal electronic band structures, but their semiconducting allotropes are less stable. In terms of chemistry, metalloids are similar to (weak) nonmetals. They have the lowest ionization energies, electron affinities, and electronegativity values. 

Residual Non-metals (Hydrogen and Selenium) 

The remaining seven nonmetals are hydrogen, carbon, nitrogen, oxygen, phosphorus, sulphur, and selenium, classified as noble gases, halogens, or metalloids (see below). Three of the gases are colourless (H, N, and O); three have a metallic look (C, P, and Se); and one is yellow (S). Graphitic Carbon is a semimetal (along its planes) electrically, while phosphorus and selenium are semiconductors and hydrogen, nitrogen, oxygen, and sulphur are insulators. 

As a result, their chemistry is taught differently depending on which of the four periodic table groups they belong to. Hydrogen, in particular, behaves like a metal in specific ways and like a nonmetal in others. It can (first) lose its single valence electron like a metal; it can stand in for alkali metals in typical alkali metal structures. It can create alloy-like hydrides with some transition metals that feature metallic bonding. 

Metals and Non-metals

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Physical Properties Of Non Metals

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• Malleability: Non-metals are not malleable, i.e. they can not be beaten into thin sheets. They are brittle, and if they are hit with a hammer, they break down quickly. The only exception is Diamond which is an allotrope of Carbon. Diamond has the highest boiling and melting point and is the hardest known substance.
• Ductility: Non-metals are not ductile, i.e. they can not be drawn into thin wires.
• Lustre: Non-metals have a submetallic or dull look except Idoine, which has a metal-like lustre.
• State: Non-metals are either solid or gases except Bromine which is liquid in the state.
• Hardness: In contrast to metals, which are shiny, ductile, and malleable, non-metals are brittle if solid. The only exception is the hardest known substance on Earth; Diamond. 
• Density: Non-metals generally have less density than metals.
• Sonorous: Non-metals are not sonorous, i.e. they do not produce sound on hitting.
• Conductors: Non-metals are poor conductors of heat and electricity, whereas graphite, another allotrope of Carbon, is an excellent conductor of heat and electricity.
• Melting and Boiling Point: The melting and boiling points of non-metals are substantially lower than those of metals (except Carbon having the highest melting and boiling point).

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Metallurgy

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Chemical Properties of Non Metals

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• The unusual Valence States

The heavier group 15–18 nonmetals have more enormous atomic radii, which allows for higher bulk coordination numbers and lower electronegativity values, which can better tolerate higher positive charges. Phosphorus pentachloride (PCl₅), sulphur hexafluoride (SF₆), iodine heptafluoride (IF₇), and xenon difluoride (XeF₂) are examples of elements that can have valences other than the lowest for their group (that is, 3, 2, 1, or 0).

• Reaction with Metals

The tendency for an element to achieve a filled valence shell is known as reactivity. To produce a cation, metal atoms lose electrons from their valence shell. An anion is formed when nonmetal atoms gain electrons in their valence shell.

For example, consider the formation of NaCl.

Sodium Cation

Na → Na⁺ + e^-

2,8,1 2,8

Chloride Anion

Cl + e^- → Cl-

2,8,7 2,8,8

NaCl

Explanation

The outermost shell of a sodium atom has one electron. If an electron is lost from the M shell, the L shell becomes the outer shell with a stable octet. This atom's nucleus still retains 11 protons, but the number of electrons has decreased to 10, resulting in a net positive charge, resulting in the sodium cation Na+.

On the other hand, Chlorine has seven electrons in its outermost shell and only needs one more to complete its octet. In a reaction between sodium and chlorine, the electron lost by sodium could be picked up by chlorine. Because its nucleus has 17 protons and its K, L, and M shells have 18 electrons, the chlorine atom has a negative charge after gaining one electron. The chloride anion Cl^– is formed as a result of this reaction.

• Ionic Compound

An ionic compound is a chemical compound made up of ions that are held together by electrostatic forces. Overall, the chemical is neutral, although it contains positively and negatively charged ions known as cations and anions. Simple ions like sodium (Na⁺) and chloride (Cl^-) in sodium chloride, or polyatomic species like ammonium (NH⁺⁴) and carbonate (CO₂^-3) ions in ammonium carbonate, are some examples. 

Individual ions in an ionic compound frequently have many nearest neighbours. Hence they are not considered molecules but rather part of a three-dimensional network. When solid, ionic substances usually form crystalline forms.

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Properties of Ionic Compounds

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Ionic compounds are formed when atoms make ionic connections with one another. The most substantial sort of chemical link is an ionic bond, which results in unique features.

• The bond has a partial positive charge on one atom and a partial negative charge on the other. Because of the electronegativity mismatch, the bond becomes polar, and some compounds are polar. Polar compounds frequently dissolve in water. Ionic compounds are therefore good electrolytes.

• Ionic substances form crystals. Rather than amorphous solids, ionic chemicals form crystal lattices. Although molecular substances can form crystals, they generally do so in different shapes than ionic crystals, and molecular crystals are typically softer than ionic crystals. An ionic crystal is a stable structure at the atomic level. The cation and anion are alternating and generating a three-dimensional structure based on the smaller ion, evenly filling up the gaps between the larger ion.

• Their melting and boiling points are extremely high. High temperatures are required to counteract the attraction between positive and negative ions in ionic compounds. As a result, ionic compounds require a lot of energy to melt or boil.

• They have higher enthalpies of fusion and vaporisation than molecular molecules. They have 10 to 100 times higher fusion and vaporisation enthalpies than typical molecular compounds. The enthalpy of fusion is the amount of heat necessary to melt a single mole of a solid under constant pressure. The enthalpy of vaporisation is the amount of heat required to evaporate one mole of a liquid substance under constant pressure.

• Because positive and negative ions are strongly attracted to one other and difficult to separate, they are hard and brittle. However, when pressure is applied to an ionic crystal, ions of similar charges may be driven closer together. Ionic solids are fragile because electrostatic repulsion is strong enough to fracture the crystal.

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Dipole Moment

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Importance of Non Metals in Daily Life

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1. Hydrogen is employed in the production of ammonia and vegetable ghee. Ammonia compounds are used as fertilizers.
2. Carbon is employed in electrolytic cells and is responsible for the growth and development of organisms because it is a significant component of vitamins, proteins, carbohydrates, enzymes, and other nutrients.
3. Ammonia, fertilizers, and nitric acid are all made from nitrogen. The rate of ignition is slowed when nitrogen is present in the air. As explosives, nitrogen compounds such as trinitroglycerin and trinitrotoluene are utilized.
4. Life and combustion processes require the presence of oxygen gas in the air.
5. In the production of gunpowder, sulphur is employed as a fungicide. Proteins, onions, garlic, wool, and other foods contain sulphur.
6. Phosphorus is used in crackers.
7. Graphite is an excellent electrical conductor.
8. Fertilizers contain potassium.
9. Bromine is used in herbicides and colours.

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Disadvantages of Non Metals

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• Non metal harms plants, reduces soil pH, and corrodes metals and structures. 
• Sulphur dioxide and nitrogen oxides can also combine with smoke and water vapours to generate smog, which harms the respiratory system and increases the risk of asthma and lung infections when inhaled. 
• Skin and eyes are irritated by these fumes.
• Phosphorus, chlorine, bromine, iodine, formaldehyde, methyl aldehyde, and methylene oxide are nonmetal compounds that function as irritant poisons and cause inflammation at the point of contact, particularly in the gastrointestinal (GI) tract, respiratory tract, and skin. 

Read More: Endothermic reactions

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Things to Remember

• Non-metals are non-malleable, non-ductile, non-sonorous, poor conductors of heat and electricity.
• Non-metal qualities are generally the total opposites of metal properties.
• Ionization energies and electronegativities are both high in nonmetals. 
• They gain electrons quickly. 
• Although they may be multicoloured, they are dull and not metallic-shiny. 
• They have lower melting and boiling points.
• Depending on the element, non-metals can be solid or gas at room temperature.
• Non-metals include sulphur, bromine, and helium.
• Nonmetals make up a small percentage of the periodic table and are usually found on the right side. 
• The exception is hydrogen, which at ambient temperature and pressure behaves like a nonmetal. 

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Exothermic reactions