Deepak sir 9811291604 Metals and Nonmetals

Deepak sir 9811291604

Metals and Nonmetals

Metals and Nonmetals

Till now, scientists have discovered 115* elements. Each of the 115 elements is unique. Each has its own fascinating story. The discovery of the elements started about 8000 years ago, when people obtained shiny materials from the rocks simply by heating. In this way, soft materials, such as copper, silver and gold were discovered. These were followed by lead, tin, iron, mercury, carbon and sulphur. When the Greek philosophers saw ordinary materials going into the foundries at Alexandria, Egypt, and large amounts of gold and silver coming out they assumed that the craftsmen were changing ordinary substances into gold and silver. Thus began the search for the philosophers' stone, a magical substance which could change any base metal into gold or silver.

CLASSIFICATION OF ELEMENTS

How are elements classified

All elements are classified into three categories.

Metals

Nonmetals

Metalloids

Metalloids are those elements which behave like both metals and nonmetals. Some common metals, nonmetals and metalloids are listed.

Where are the metals, nonmetals and metalloids located in the Periodic Table Metals are placed on the left-hand side, in the middle and at the bottom of the Periodic Table. Nonmetals are placed on the right hand side and in the upper middle part of the Periodic Table. The location of nonmetals is shown by yellow colour. Metalloids are located at the left end of the nonmetals. The location of metalloids is shown by dark yellow colour. The noble gases are present on the extreme right side of the Periodic Table. What are metals Metals are the elements (except hydrogen) which form cations (positive ions) by losing electrons. Thus, metals are electropositive elements. Gold, silver, copper, tin, lead, iron, mercury are typical metals. These metals were known to the ancient people. What are nonmetals The elements which tend to form anions (negative ions) by gaining electrons are termed nonmetals. There are 22 nonmetals.

Most nonmetals are gases. Some nonmetals occur as solids. Bromine is the only nonmetal which occurs as liquid under normal conditions. Solid nonmetals -- Carbon, Sulphur, Phosphorus, Iodine Liquid nonmetal -- Bromine Gaseous nonmetals -- Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine What are metalloids The elements which behave like metals as well as nonmetals are called metalloids. Boron (B), Silicon (Si) and Arsenic (As) are metalloids. How is the metallic and nonmetallic character of an element related to its electronic configuration The chemical properties of any element depend upon its electronic configuration. So, whether an element behaves like a metal or nonmetal depends upon its electronic configuration. Thus, a metal and a nonmetal differ in their electronic configurations. Metals generally have 1 to 3 electrons in the outermost shell (or valence shell) of their atoms. Nonmetals usually have 4 to 8 electrons in the outermost shell (or valence shell) of their atoms. Hydrogen and helium, however, do not follow this rule. To illustrate these rules, let us write the electronic configurations of some typical metals and nonmetals. Let us take sodium (Na), magnesium

(Mg) and aluminium (Al) as typical metals, and carbon (C), nitrogen (N), oxygen (O), fluorine (F) and neon (Ne) as typical nonmetals.

Thus, we see that metals have 1 to 3 electrons, whereas nonmetals have 4 to 8 electrons in their outermost (or valence) shells. Hydrogen (H) and helium (He) are exceptions to this rule. Hydrogen (H) and helium (He) are nonmetals. Hydrogen has only one electron in its outermost (or valence) shell, i.e. hydrogen has only one electron in its K-shell. Helium (He) has two electrons in its outermost (or valence) shell, i.e. helium has two electrons in its K-shell.

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Deepak sir 9811291604

Metals and Nonmetals

What are the general uses of metals Some general uses of metals are described below. > Copper and aluminium are very good conductors of electricity. So, copper and aluminium are used for making electrical wires and cables.

Aluminium is also used for making cooking utensils. Aluminium foils are used for packaging of medicines, food materials, etc.

Iron is the most widely used metal. Its uses, however, mainly depend upon its carbon content. For example, Cast iron is used for manufacturing wrought iron and steel. It is generally used for making stove burners, gutter pipes, railway sleepers,

etc. Steels are used for the manufacture of permanent magnets, engine parts, utensils, surgical equipments, springs, gears, drive shafts,

armour plates, etc. Wrought iron is used for making anchors, wire ropes, bolts, chains and agricultural appliances.

Zinc is used for the galvanisation of iron. Tin is used for tinning of iron plates/sheets and copper/brass utensils. Thus, zinc and tin are used

for protecting iron from rusting.

Nickel and chromium are mainly used for electroplating and for the manufacture of stainless steel. Nickel is also used as a catalyst in many

industrial processes.

Gold and silver are used for making jewellery and for decorative purposes.

Sodium, titanium and zirconium are used in atomic energy and space science projects. Zirconium is used for making bullet-proof alloy

steels.

Mercury is used in thermometers and barometers.

Titanium is used in

aerospace

aircraft frames and engine

military hardware

marine equipment

chemical reactors

chemical industries

atomic energy and space science projects

Titanium, due to its special applications, is considered as a strategic metal, These applications of titanium are due to its

high tensile strength

lightness

resistance to corrosion

high melting and boiling points

ASSIGNMENT I

Classification of elements, Location of metals, nonmetals and metalloids in periodic table, General uses of metals

1. Name the three categories in which all the elements are classified.

2. Identify metals from the following list:

Silicon, Carbon, Sulphur, Oxygen, Copper, Mercury, Zinc, Boron, Phosphorus

3. Where are metals located in the Periodic Table?

4. How is the metallic and nonmetallic character of an element related to its electronic configuration?

5. Which of the following is a metal?

6. Mention two uses of aluminium. 7. Name the metal that is used for making bullet-proof steels. 8. Mention two uses of nickel. 9. Why are metals such as titanium, vanadium, chromium, etc. considered strategic metals? COMPARING METALS AND NONMETALS What are the physical properties of metals All metals show some common physical properties. There is however, some variation in each property from metal to metal. Metals are malleable. This means that metals can be hammered into very thin sheets. Gold and silver are among the most malleable metals. Both gold and silver can be hammered into foils much thinner than the thinnest paper. Metals are ductile. This means that metals can be drawn into thin wires. All metals are not equally ductile, i.e. some metals are more ductile whereas others are less ductile. Gold, silver and copper are among the most ductile metals. For example, we can draw a wire of about 200 m length from 100 mg of silver. Metals are good conductors of heat and electricity. Metals permit heat and electricity to pass through them. Silver, copper and aluminium are good conductors of heat and electricity. Silver is the best conductor of electricity. Copper is the next best conductor of electricity. Gold, aluminium and tungsten are good conductors of electricity after silver and copper. Mercury and iron offer greater resistance to the flow of current. Therefore, mercury and iron are not good conductors of electricity. Copper and aluminium are used for making electric wires/cables because they are very good conductors of electricity. Metals are lustrous. This means that metals are shiny. The characteristic shine of metals is called metallic lustre. Metals can be polished.

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Metals and Nonmetals

Metals have high tensile strength. Metals are very strong. They can bear a lot of stress.

Most metals except sodium and potassium are hard. Sodium and potassium metals can be easily cut with a knife. Osmium is hard enough

to scratch glass.

Most metals except sodium and potassium have high melting and boiling points. The melting and boiling points of some common metals

are given below.

Metal

Copper Iron Silver Sodium Potassium

Melting point/?C : 1083 1539 960.8 97.9

63.8

Boiling point /?C : 2310 2450 1955 882

760

(h) Metals, except sodium and potassium, have high densities. Most metals have high densities. Sodium and potassium have much lower

densities. The densities of some common metals are given below:

Metal :

Copper Iron Silver Gold Sodium Potassium

Density, g/mL : 8.94 7.86 10.47 19.5 0.97

0.86

Metals are sonorous. Metals when hit by a hammer produce a characteristic metallic sound.

All metals except mercury are solids. Under normal conditions, all metals are solids. Mercury is the only metal which is liquid under

normal conditions.

Metals can form alloys with other metals. Metals can form homogeneous mixtures with other metals. Such solid homogeneous mixtures

are called alloys. For example, copper and zinc dissolve in each other to form an alloy called brass.

PHYSICAL PROPERTIES OF NONMETALS

What are the general physical properties of nonmetals

Some common/general physical properties of nonmetals are described below:

Nonmetals are brittle. Solid nonmetals break up into pieces when pressed hard or hammered. For example, sulphur and red phosphorus

are brittle.

Nonmetals are neither ductile nor malleable. Solid nonmetals cannot be drawn into wires, and beaten into leaves / sheets because they are

brittle.

Nonmetals are insulators. Nonmetals do not conduct heat and electricity. This is because they do not have free electrons. However,

graphite is a good conductor of heat and electricity.

Nonmetals do not have lustre. Nonmetals are not shiny. However, graphite and iodine are the only nonmetals which have metallic lustre.

As a result, nonmetals cannot be polished.

Nonmetals usually have low densities and are soft. Diamond (an allotrope of carbon), however, is an exception. Diamond is the hardest

natural substance known.

Nonmetals have low tensile strength. Solid nonmetals can be easily broken.

Nonmetals have low melting and boiling points. However, graphite has a high melting point (3700 ?C). Sulphur and phosphorus have low

melting points--white phosphorus melts at 44?C, and sulphur melts at I15?C.

Nonmetals are nonsonorous. Nonmetals do not produce sound when hit with an object.

Nonmetals may be solid, liquid or gaseous at room temperature. For

example, under room temperature conditions, sulphur and phosphorus are solids, bromine is liquid, whereas hydrogen, oxygen and

nitrogen are gases.

Nonmetals show allotropy. The property of an element to exist in more than one structural form is called allotropy. The different forms of

an element are called allotropic forms or allotropes.

Some nonmetals can exist in more than one form, i.e. they exist in more than one allotropic form. For example,

* Phosphorus exists in five different forms, viz. white or yellow phosphorus, and lamp black are allotropes red phosphorus, violet

phosphorus, black phosphorus and scarlet phosphorus.

Carbon exists in the following allotropic forms, viz. diamond, graphite, coal, coke, lamp black, etc.

Sulphur also exists in various allotropic forms, viz. rhombic sulphur, monoclinic sulphur, plastic sulphur, etc.

Home work 2 1. Name a nonmetal which has only one electron in its outermost shell.

2. Which of the following is a nonmetal? 3. Why are nonmetals electronegative in nature? 4. Name a nonmetal which is a good conductor of heat and electricity. 5. Name two nonmetals which are both brittle and nonductile. 6. From the following list, choose metals and nonmetals. State the property on the basis of which you made your choice: Chlorine, Aluminium, Sulphur and Magnesium 7. Name three nonmetals which show allotropy.

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Metals and Nonmetals

8. Name one metal and one nonmetal which are liquid at room temperature? 9. What is meant by the term malleability of a metal? 10. Give two examples of metals which are malleable as well as ductile. 11. Give reason for the following: Metals conduct electricity.

CHEMICAL PROPERTIES OF METALS What are the chemical properties of metals Metals are electropositive elements. In chemical reactions, metals lose electrons to form positively-charged ions (called cations). The reactivity of a metal depends upon its nature and the reaction conditions. Some typical chemical reactions of metals are described below. How do metals react with oxygen All metals combine with oxygen to form metal oxides. The reactivity of a metal towards oxygen depends upon its nature. For example, (i) Sodium reacts with oxygen at room temperature to form sodium oxide.

(ii) Magnesium does not react with oxygen at room temperature. On heating in oxygen/air, magnesium burns with a dazzling white light to give magnesium oxide.

Reaction conditions of metals with oxygen

(iii) Zinc reacts with oxygen only on strong heating. Zinc burns with a bluish flame when heated strongly with oxygen.

(iv) Iron reacts with oxygen on strong heating without burning.

(v) Copper reacts with oxygen slowly only on prolonged strong heating.

The reaction conditions for the reactions of sodium, magnesium, zinc, iron and copper with oxygen, it is clear that sodium reacts most readily with oxygen, whereas copper reacts least readily with oxygen. Thus, here sodium is the most reactive metal and copper is the least reactive metal. So, the order of reactivity of these metals with oxygen is Na > Mg > Zn > Fe > Cu

most reactive -------------------------------------------------------> least reactive reactivity decreases

How is a metal oxide formed When a metal reacts with oxygen, it loses its valence electrons to form a positive ion (cation). On the other hand, an atom of oxygen gains two electrons to form oxide (O2-) ion. These two oppositely charged ions combine together to form an ionic metal oxide. For example, magnesium (Mg) reacts with oxygen to form magnesium oxide as follows:

What is the nature of metal oxides

Metal oxides are basic or amphoteric depending upon the nature of metal.

The oxides of metals such as sodium, potassium, calcium, magnesium, etc., are basic in nature.

The oxides of metals such as aluminium, zinc are amphoteric in nature. Soluble metal oxides react with water to give metal hydroxides

(alkalis). The solutions of metal oxides in water turn red litmus blue, and colourless phenolphthalein to pink. For example, sodium oxide

(Na20) reacts with water to give sodium hydroxide.

Na20 + H20 ------------------> 2NaOH

sodium oxide

sodium hydroxide

(basic oxide)

(alkaline in nature)

Sodium hydroxide solution, so formed, turns red litmus blue. Red litmus + NaOH -----> Blue litmus

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Metals and Nonmetals

Phenolphthalein+ NaOH------ Pink colour (colourless) Calcium oxide (CaO) dissolves in water to give Ca(OH)2(aq). Ca(OH)2(aq) is called limewater. It is basic in nature. It also turns red litmus blue. Some metal oxides, e.g., aluminium oxide (A1203), zinc oxide (ZnO) show both acidic as well as basic character. These metal oxides are called amphoteric oxides. For example,

How do metals react with water Different metals react with water under different conditions. Some metals react with cold water, whereas some other metals react only with hot water, or steam at red heat. Some metals do not react with steam even at red heat. Reactions of some common metals with water are described in Table.

From the results obtained above, we see that sodium reacts with cold water, magnesium reacts with boiling water, aluminium reacts slowly

with boiling water, zinc decomposes boiling water slowly but steam rapidly, iron reacts with steam only at red heat, copper does not react

even with steam on heating strongly. Thus, we conclude that

Magnesium is less reactive than sodium.

Aluminium is less reactive than magnesium.

Zinc is less reactive than aluminium.

Iron is less reactive than zinc.

Copper is less reactive than iron.

Therefore, the order of reactivity of these metals with water is

Na > Mg > Al > Fe > Cu

most reactive

-> least reactive

reactivity decreases

How do metals react with dilute acids

Usually metals displace hydrogen from dilute acids. The less reactive metals, such as copper, silver, gold, etc. however, do not displace

hydrogen from dilute acids.

The reactions of metals with dilute hydrochloric acid and dilute sulphuric acid are similar. In both the cases, hydrogen is given out and the

corresponding salt is formed. Thus,

Metals react with dilute hydrochloric acid to give metal chloride and hydrogen gas.

Metals with dilute sulphuric acid give metal sulphate and hydrogen gas.

With nitric acid, metals do not produce hydrogen gas. This is because nitric acid is an oxidising acid. The nature of the products formed

depends upon the nature of the metal and the concentration of nitric acid.The reactions of some metals with HCI and H2S04 in Table .

Thus, we see that the rate at which a metal reacts with a dilute acid depends upon the nature of the metal, i.e.

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