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Class 10 Science chapter 3 metals and non-metals notes

CHAPTER 3  METALS AND NON-METALS.

METALS –

              Metals are the substances which are electropositive in nature is, they have a tendency to lose electrons.

All metals except mercury exist as solids room temperature.

About 118 elements are known today. There than 90 metals, 22 non-metals and a few metalloids. For example – Sodium (Na), Potassium (K), magnesium (Mg), aluminum (Al), calcium (Ca), Iron (Fe) Barium (Ba) are some metals.

PHYSICAL PROPERTIES OF METALS –

1. Metals in their pure state, have a shining surface. This property called metallic lustre. Like – Gold, Silver etc..

2. Metals are generally hard. The hardness waves from metal to metal.

3.Some Metals are malleable – Metals which can be beaten. into thin sheets, this property is called malleability.

     Gold and silver are the most malleable metals.

4. Some metals are ductile. – The ability of metals to be drawn into thin wires is called ductility.

Gold (most-ductile about 2km length can be drawn from one gram of gold).

5. Metals are good conductor of heat. (Best – silver and copper) like aluminum in corking vessels.

6. Metals have high melting and boiling point.

– Tungsten has the highest melting point where as silver has low boiling point.

– Sodium and potassium have low melting point.

7. Metals are good conductor of electricity, like copper, aluminum etc.

Some metals are used to coat the electrical wires are polyvinylchloride (PVC) of a rubber like material.

8.Some metals are sonorous –

The metals that produce a sound on striking a hard surface are called sonorous.

9.Metals have high density and are very heavy, iridium and osmium have highest densities where lithium has the lowest density.

#WHAT IS NON METAL?

There are the substances which are electronegative in nature ,

i.e tendency to gain electrons.

There are example have 22 non- metals.

Examples – carbon, Sulphur, iodine, oxygen, hydrogen etc.

The non- metals are either solids or gases except bromine which are is a liquid

* PHYSICAL PROPERTIES OF NON-METALS.

1. Non-Metals are non-lustrous (no shine)

2. They are not sonorous.

3.Non-Metals are not malleable.

4. Non-Metals are not ductile

5.They are poor – conductor of electricity

6.Non-Metals are soft.

7.They have too low density.

#EXCEPTION TO METAL & NON-METAL PHYSICAL PROPERTIES –

1.All metals except mercury at room temperature. exist  as solid at room temperature

2.Gallium and cesium (metals)  have very low melting points.

3 Iodine is a non- metal but it is lustrous.

4.Carbon is a non-metal that can exist in different forms.

Each form is called an allotrope. like diamond-hardest natural substance, very high

 melting point and polling point. Graphite , allotrope of carbon is a conductor of electricity.

5. Alkali metals (lithium, sodium, potassium) are so soft, have low densities, and low

melting points.

#QUESTIONS

 Give an example of a metal

(i)which liquid at room temperature. – Mercury

(ii) can be easily cut with a – Sodium

(iii) is the best conductor of heat. – Silver

(iv) is a poor conductor of heat Mercury & lead.

# Chemical Properties of Metals

Metal’s reaction with oxygen –

Almost all metals combine with to form metal oxide.

Metal +Oxygen →Metal Oxide

(for example – When copper is heated in air, it combines with  oxygen  to form Copper Oxide,

a black oxide.)

2Cu+O₂—2CuO

Aluminum forms aluminum oxide

4Al + 3O₂ → 2Al₂O₃

→ When copper oxide reacts with hydrochloric acid it produced salt and water.

Means here copper oxide or  metal oxides are both in basic nature..

CuO + 2HC1→ CuCl₂+ H₂O

                           (salt)  ( water)

Some metal oxide such as aluminum oxide, zink oxide etc. show both acidic and basic  behavior. when there metal oxides react with base, then they act like acid, and when these metal oxide reacts with acid, then they react like bases. Those type of metal oxides are called amphoteric oxides.

Al₂O₃+6HCL→ 2AlCl₃+3H2O

(base)   (acid)     salt            water

Al₂O₃+2NaOH→2NaAlO2+H2O

Acid        base       salt            water

                                   (sodium aluminate)

→Most metal oxides are insoluble in water but some these dissolve in water to form

alkalis. Sodium oxide and potassium oxide. dissolve in water to produce alkalis.

Na₂O(s) + H₂O(l) →2NaOH

K₂O (S) + H₂O(l) →2KOH(aq)

 #REACTIVITY OF METALS TOWARD OXYGEN-

  1. Potassium and Sodium. Highly reactive in air, they kept in the open, they catch fire.

Hence, to protect them and to prevent accidental fire, they are kept in Kerosene oil.

     2.Magnesium, aluminum, zine, lead – are covered with thin layer of oxide, the protective

         layer prevents the metal from further oxidation.

     3.Iron – It does not burn on heating but iron filings burn vigorously heating.

4. Copper – Copper does not burn, but the hot Metal layers is coated with a black colored

copper oxide.

5.Silver and Gold – They do not react with oxygen even at high temperature.

So Sodium is the most reactive metal.

(2) Metals react with Water

When Metal react with water and produce a metal oxide and hydrogen gas.

Metal oxide that are soluble in water dissolve in It are to further form metal hydroxide.

Metal + Water → Metal oxide + Hydrogen

Metal oxide + Water →Metal hydroxide

Metals like potassium and sodium react violently with cold water.

 In case of sodium and potassium, the reaction is so violent and exothermic that the

evolved hydrogen immediately catches fire.

2K (S)+ 2H₂O (1) → 2KOH (ag) + H₂(g) + Heat

2 Na (s) + 2H₂O (1)→ 2NaOH (aq) + H₂ (g)+ Heat

The reaction of calcium with water is less violent . the heat evolved is not sufficient for

 the hydrogen to catch fire.

Ca(s) + 2H₂O (1)→ Ca(OH)₂ (aq) + H₂(g)

Calcium starts floating because the bubbles of hydrogen gas formed to the surface of the metals.

→ Magnesium does not react with cold water. It reacts with hot water to form magnesium hydroxide and hydrogen gas and starts floating due to the bubbles of hydrogen gas.

Mg+2H₂O—Mg(OH)₂+H₂

Aluminum, iron and zink do not react either with cold or hot water.

But they react with steam to form the metal oxide and hydrogen.

2Al (S) + 3H₂0 (g) → Al₂O3 (s) + 3H₂(g)

3fe (s) + 4H20 (2) → Fe₂O4 (s) + 4H₂ (g)

Metals such as lead, copper, silver and gold do not react with water at all.

[3] Metals react with acids-

Metal react with acid to give salt and hydrogen gas.

Metal+ Dilute acid→ Salt+ Hydrogen gas

when magnesium, aluminum, zine and iron react with HCl they produce salt and

hydrogen.

Metal + HNO3→H2-X

Hydrogen gas is not evolved when a metal reacts with nitric acid.

It is because HNO3 Is a strong oxidizing agent.

But Magnesium (mg) and manganese (mn) reacts  with very dilute

HNO3 to evolve H2 gas.

→ The rate of formation of bubbles is the fastest in case of magnesium.

The reaction is so the most exothermic in this case.

Reactivity decreases in order

Mg > Ad > Zn > Fe.

Copper- does not reacts with dilute HCL, so no bubbled were formed.

[4] Metals react with Solutions of other metal Salts

-In this case Reactive metals can displace less reactive metals from their compounds in

solution or molten form.

→ Displacement reaction occured in the case. If metal A displaces metal B from its

solution, It more reactive than B.

Metal A +Salt Solution of B → Salt solution of A+ Metal B.

CuSO4+FeSO4   →   FeSO4+CuSO4

Fe+CuSO4→FeSO4+Cu

Cu+FeSO4→CuSO4+Fe

[5] Reactivity series-

K    Potassium           Most reactive

Na   Sodium

Ca   Calcium

Mg   Magnesium

Al    aluminum

Zn    zinc                  reactivity decreases

Fe    iron

Pb   lead

H    hydrogen

Cu   copper

Hg   mercury

Ag   sliver

Au   gold                   least reactive

SOME IMPORTANT TERMS-

  1. Anodising

   Anodising is process of forming a thick oxide layer of aluminum.

This aluminum oxide coat makes it resistant to further corrosion(makes Al₂O3)

  The resistance can be improved further by making the oxide layer thicker.

During  anoding, a clean aluminum article is made the anode and Is electrolyzed

with dilute sulphuric acid.

The oxygen gas evolved at the anode reacts with aluminum to make a thicker proactive oxide layer.

2. Aqua regia –(Royal water)

-It is a freshly prepared mixture of concentrated hydrochloric aic and concentered nitic

acid in the ratio of 3:1.

-the solution is used for dissolving gold

-it is one of the few reagents that is able to dissolve gold and platinum.

#QUESTIONS

Q-1 Why is sodium kept in kerosene oil?

Ans- because sodium is the most reactive metal.

And  Metal +HCl→ Salt + H2 gas

 Que -2 Write the chemical reaction when iron reacts with dilute H2SO4.

Ans   Fe + H2SO4 → FeSO4 +H2

When a metal and non-metal reacts with each other transfer of electrons take place from metal to non-metals.

→ Compounds that are formed by the transfer of ions are known as ionic compounds.

→ They have strong electrostatic force of attraction.

  Electronic configuration of elements

 *NOBLE GAS-

Compounds which have  a completely  filled valence shell, and show little chemical activity like

Helium(He)—         k-2

Neon (Ne)—           k-2  L-8   Etc.

*METALS –

sodium (Na)            k-2   l-8    m-1

Magnesium(mg)     k-3   l-8    m-3

*NON METALS –

Oxygen (O)           k-2 l-6

Chlorine(Cl)          k-2 l-8  m-7

FORMATION OF SODIUM CHLORIDE –

  Sodium (metal) is electro-positive and reducing agent. So it will lose one electron from its outer shell.

  Chloride (non metals) is electro -negative and oxidizing agent. So it will gain one electron by sodium.

 Na      →     Na+  +  e

(2,8,1)            (2,8)

 (sodium cation)

Cl + e-→  Cl-

(chloride anion)

  • Formation of magnesium chloride-

Mg → Mg2+ + 2e-

           (2,8,2)    (2,8)

          (magnesium cation)

    Cl+ e-→Cl-(chloride anion )

*PROPERTIES OF IONIC COMPOUNDS-

I) PHYSICAL NATURE-

                  ionic compounds are solid and are somewhat hard because of the strong force of attraction between the positive and  negative ions. compounds are brittle, and break into pieces when pressure is applied.

II) MELTING  AND BOILING POINT-

    ionic compounds have high melting and boiling point.

III) SOLUBILITY-

      Electrovalent compounds are . generally soluble in water and insoluble solvents such

      as  kerosene, petrol etc.

(IV)CONDUCTION OF ELECTRICITY-

       The conduction of electricity through a solution involves the movement of charged

       particles .A solution of an ionic compound in water contains ions, which move to the

       opposite electrodes when electricity is passed through the solution.

→ Ionic compounds the solid state do not conduct electricity because movement of ions in

solid is not possible.

 →Ionic compounds conduct electricity in the molten state.

Because electrostatic. forces of attraction between the oppositely charged ions are overcome due to the heat. Thus, the ions moves freely and conduct electricity.

Cathode→ Reduction→ Gain of electron Oxidation

Anode→ Oxidation→ Loss of electron

Q 1) (a)electron -dot structure of oxygen

               O2(2,6) →

 (b) Formation of Na2Oand MgO by the transfer of electrons

Q 2) why do ionic compounds have high melting point?

Ans: Because ionic compounds have strong force of attraction so they need a considerable amount of energy is required to break the strong inter- ionic attraction.

* OCCURRENCE OF METALS –

Earth’s  crust is the major source of metals, the elements or compounds, which naturally in the earth’s crust occur known as minerals.

– When Minerals contain a very high percentage of a particular metal and the metal can be profitably extracted from it. These minerals are called ores.

EXTRACTION OF METALS –

Some metals. Are found in the earths crust in the free state. Some are found in the form of their compounds.

   The metals at the bottom of the activity series are the least reactive .

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