Metals are elements that conduct heat and electricity. They are malleable and ductile. Metals are also lustrous, hard, strong, heavy and sonorous. Some of the metals are Iron, Aluminum, Copper, Silver, Gold, Platinum, Zinc, Tin, Lead, Mercury, Sodium, Potassium and Magnesium.All the metals are solids, except mercury which is a liquid at room temperature. During chemical reactions, metals can form positive ions by losing electrons. Based on this observation, we can write another definition of metals."Metals are the elements which form positive ions by losing electrons."
They are also known as electropositive elements. The most abundant metal in the earth’s crust is aluminium. The second most abundant metal in the earth's crust is iron. Metals are present on the left side of the periodic table. They have a number of uses in our daily life. The cooking utensils, electric wires, sewing machines, cars, trains, ships and aeroplanes are all made up of metals or a mixture of metals called alloys.
Characteristics of Metals Nonmetals and Metalloids
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An element is a pure chemical substance consisting of the same type of atom. The periodic table is the latest arrangement of all the discovered elements on the basis of their atomic number. As of November 2011, 118 elements have been identified and placed in the periodic table. Out of these 118 elements, 98 are present naturally on earth in the form of their different compounds. Out of these elements, 80 elements are stable and 18 are unstable & radioactive in nature.
Periodic Table Metals Nonmetals Metalloids
All elements show specific chemical and physical properties. Briefly, all elements can be classified as metals, non-metals and metalloids. In a periodic table, metals are arranged on the left side and non-metal on the right side, while metalloids are present as a connecting line between metals and non-metals. Boron, silicon, germanium, arsenic, antimony and tellurium are included among the metalloid category. Metalloids are also known as semi metals. Out of all the known elements, more than 75% elements are metallic in nature.
|| Have lustrous surface
|| Some have luster
|| Dull appearance
|| Have high melting point
|| Intermediate value
|| Low melting point
|| High density
|| Intermediate value
|| Low density
|| Solid at room temperature
|| Generally solid
|| Solid , liquid and gas form
|| Good conductor of heat and electricity and heat
|| Become conductor at certain temperature
|| Can be drawn in sheet (malleable)
|| Non malleable
|| Non malleable
|| Can be drawn in wired(Ductile)
|| Brittle in nature
|| Brittle in nature
|| Opaque in nature
|| Vary from element to element
|| transparent (can see through non-metal)
|| Non- sonorous
|| Non- sonorous
Silicon is a gray color solid at room temperature with a very high melting point and boiling point and metallic luster. Under normal conditions, its a good conductor of heat, and hence cannot be used to insulate hot objects. All these features make it closer to metals. Since the valence shell electronic configuration of silicon is 3s2, 3p2, hence it can readily accept or lose four electrons to get a noble gas configuration. This character gives a non-metallic nature to silicon. Silicon makes a cubic crystal structure after crystallization just like diamonds. Hence silicon is a metalloid with intermediate features.
Calcium is a dull gray solid element with a silver appearance, which exists in the solid state. It has a high melting point (1115 K) and boiling point (1757 K). All these features make it related to metals. The valence electron configuration of calcium is 4s2, hence it has a tendency to loose two electrons to get a Noble gas configuration.
Since it can lose electrons, it can be used in ionic bonding and can form ionic compounds. Like other metals, calcium also reacts vigorously with dilute acids like hydrochloric acid and produce large amounts of heat, forms calcium chloride (CaCl2) and hydrogen gas. All these properties of calcium prove that calcium is a metal.
Sodium is a silvery white solid element with silvery luster. Sodium is a soft element that can be easily cut with a knife. Its a very good conductor of electricity and heat. It shows very low electronegativity (0.93 (Pauling scale)) and low first ionization energy (495.8 kJ-mol-1). But the second ionization energy is very high (4562 kJ·mol-1), which proves that its easy for sodium to lose one electron and form a sodium ion. But removal of a second electron requires a high amount of energy, as the second ionization energy for sodium is 4562 kJ·mol-1.
Sodium metal reacts with water to produce sodium hydroxide (NaOH) and hydrogen gas. By adding Phenolphthalein to the same solution, it turns purple in color. It proves that sodium hydroxide is a strong alkali.
2Na + 2H2O $\rightarrow$ 2NaOH + H2
All features like low ionization energy, low electronegativity, solid state & conductivity prove that sodium is a metal.
We are familiar with gold jewellery and utensils. Gold is an element with the atomic number 79. It's a d-block element in the periodic table.
- Gold is a dense but a soft, shiny element. The properties like malleability and ductility include it in the metal class. It shows high melting point (1337.33 K) and boiling point (3129K).
- The electronic configuration of gold is [Xe] 4f14 5d10 6s1 , hence its a part of the d-block elements and shows variable oxidation states, like -1, 1, 2, 3, 4, 5.
- Instead of making a basic oxide like metals, oxides of gold are amphoteric in nature. It's a native & very less reactive metal. Hence it does not react with dilute acids under normal condition.
- But it reacts with aqua regia. Aqua regia is formed by mixing nitric acid and sulfuric acid in 3:1 ratio. It's an extremely corrosive acid that is able to react with metals such as gold and platinum, and produce nitrate salt of metal with brown color NO2 gas.
Au(s) + 6HNO3(aq) $\rightarrow$ Au(NO3)3 (aq )+ 3NO2(g )+ 3H2O (l )
Properties of Metal-Nonmetals And Metalloids
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(a) Properties of metals
Almost all metals which have low ionization energies and low electro negativities are electropositive in nature and have a tendency to lose electrons. Hence they are a good reducing agent.
All metals show different reactivity towards various regents. Like alkali metals, alkaline earth metals are highly reactive and react vigorously with water and dilute acids. But transition elements are less reactive compared to alkali metals.
Some general properties of metals are:
1. Metals react with air to form oxides:
2M + O2 $\rightarrow$ 2 MO
The reactivity varies from metal to metal. Some metals, like beryllium and magnesium, react vigorously with air and form oxides. Magnesium burns with a typical intense white flame, while calcium is quite reluctant to start burning, but then bursts dramatically into flame, burning with a white flame.
2Mg + O2 $\rightarrow$ 2MgO
Ca + O2
Some metals like copper and silver do not react vigorously, but take time.
Cu + O2
Ag + O2 $\rightarrow$ Ag2O (Grey)
Once the oxide layer coats the metal surface, it will prevent further attack of oxygen. That is the reason, some metals like aluminum are reluctant to reaction with air.
2. Metals react with water to form hydroxides and hydrogen gas
Alkali metals reacts vigorously with water to produce hydrogen gas and an alkaline solution.
2Na(s) + 2H2O(l)
$\rightarrow$ 2NaOH(aq) + H2(g)
2Li(s) + 2H2O(l) $\rightarrow$ 2LiOH(aq) + H2(g)
Alkaline earth metals are less reactive than alkali metals. For example, calcium reacts quickly with water to form calcium hydroxide and the bubbles you see in the beaker are because of hydrogen gas. The solution turns milky white in color because of the precipitation of calcium hydroxide.
Ca + 2H2O
$\rightarrow$ Ca (OH) 2 + H2
As we move down the reactivity series of metals, their reactivity towards water decreases. Like aluminium does not react with cold water but forms aluminium oxide and hydrogen gas with steam. Less reactive metals like iron, zinc show no reaction with cold water but form oxides with steam and form oxides and hydrogen gas but reaction will be much less vigorous.
3. Metals react with non-metals to form ionic compounds
Since metals are electropositive in nature hence they can easily loos electron and form a metal cation. On the contrary, non-metals are electronegative and form anions. The cation and anion combine together by electrostatic force of attraction known as ionic bond and such compounds are termed as ionic compounds. For example, sodium metal reacts with fluorine to form sodium fluoride.
4. Metals react with acid to form salt and hydrogen gas
Reaction of metal with acid depends on their reactivity. Highly reactive metals can react with dilute acids and release hydrogen gas while less reactive metals react with strong acid under drastic conditions only. For example, magnesium strip reacts readily in dilute sulfuric acid and forms magnesium sulphate and hydrogen gas.
Mg(s) + H2SO4 (l)
$\rightarrow$ MgSO4(s) + H2 (g)
(b) Properties of non-metals
There are only 17 non-metals (excluded H) arranged at right in the periodic table. They are electronegative elements with high electronegativity and ionization energy. They have a tendency to accept electrona and form anions.
Non-metals react with oxygen to form non-metallic oxides, which are acidic in nature. Hence non-metallic oxides form an acidic solution when dissolved in water and turn litmus solution red. For example, carbon is oxidized to form carbon dioxide, which is acidic in nature.
C(s) + O2 (g) $\rightarrow$ CO2 (g)
Non-metals are good oxidizing agents and are oxidized in almost all of their reactions. Like aluminum is oxidized with bromine to form aluminum bromide.
Non-metals have a tendency to oxidize metals.
$\rightarrow$ 2 MgO(s)
They can easily oxidize those compounds with which they react.
2H2S (g) +3O2 (g)
$\rightarrow$ 2SO2 (g) + 2 H2O (g)
Less electronegative non-metals like carbon & hydrogen can act as a reducing agent for some compounds like ferric oxide, copper (II) oxide.
Fe2O3(s)+3 C(s) $\rightarrow$ 2 Fe(s)+3 CO(g)
CuO(s)+H2(g) $\rightarrow$ Cu(s)+H2O(g)
Generally, no reaction takes place between non-metals and acids. But non-metals react with bases to form salts. For example, chlorine reacts with calcium hydroxide to form bleaching powder.
(c) Properties of metalloids
- Metalloids tend to show an intermediate property between metals and non-metals. Some metalloids like arsenic and antimony are crystalline solids.
- However, the chemical properties of metalloids are either as metals or non-metals. They form amphoteric oxides as metals form basic oxides but non-metals are generally acidic oxides.
- The most important feature of metalloids is their semi conductivity. Some metalloids like boron, silicon and germanium behave as semiconductors.
- The chemical reactivity of metalloids depends on the substance they react with. For example, when boron reacts with fluorine, it acts as a metal. While in reaction with sodium, it acts as a non-metal.
- Metalloids are usually brittle in nature and behave as electrical insulators at room temperature but act as a conductor at a certain temperature. They are used as do-pants in glasses in semiconductor chips.