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10 Class- Periodic Classification of Elements

Periodic Classification of Elements

In year of 1800 about 30 elements were known but at present we know about 114 elements. All these elements have different properties. So to study about these elements easily, scientists start searching some patterns in the properties to arrange these elements.

Early Attempts in the Classification of Elements

                                                                   This is practice to arrange elements in order out of chaos, means arranging elements in group of metals and non-metals. Chaos means complete disorder or confusing. Furthermore attempts were made to achieve best classification of the elements.

Dobereiner’s Triads

                             A German chemist, Johann Wolfgang Dobereiner in 1817 tried to arrange elements in the group of 3-elements in each group with similar properties and he called these groups as ‘Triads’. Dobereiner shows that when we take any triad and arrange its elements in the order of increasing atomic masses then the atomic mass of the middle element in the triad is roughly equal to the average of the 1st and 3rd element of the triad.

Dobereiner Triads

In first triad Li, Na, K atomic mass of   Na (23) = [ Li(7) + K(39)]/2

Newlands Law of Octaves

                                      An English scientist, John Newlands in 1866 arranges known elements in order of their increasing atomic masses. At that time he started with Hydrogen as 1st element with lowest atomic mass and ended at Thorium as 56th element.  John Newlands observe that the property of every eighth element  is similar to that of first element and compare this to octaves of music so he called it ‘Law of Octaves’ and this is known as ‘Newlands Law of Octaves’.

Newlands Octaves

Co and Ni
Ce and La

1.     Newlands law of octaves is applicable only up to Calcium and after Calcium it is not applicable because after Calcium every eighth element is do not similar to that of first element. 
2.     Newlands assumed only 56 elements exists in nature but later several elements discovered whose properties are very different to get fit in Newlands law of octaves. 
3.     With the discovery of new elements, Newlands try to fit these elements in octaves so he put two elements in same slot and Newland also put elements with different properties in same slot for example Co and Ni placed in F, Cl column.

Mendeleev’s Periodic Table

                                      A Russian chemist, Dmitri Ivonovich Mendeleev in 1872 published his ‘Mendeleev Periodic Table’ in a German journal.  He arranges elements in the form of table on the basis of fundamental property of elements i.e. atomic mass and also on the basis of similarity of chemical properties of elements, means elements with similar chemical properties are placed together in table.

Mendeleev Periodic Law

                             According to this law “the properties of elements are the periodic function of their atomic masses”.
In Mendeleev periodic table horizontal rows are called as ‘Periods’ and vertical columns are called as ‘Groups’.

Mendeléev’s Periodic Table

10th Class- Mendeleev periodic table, Periodic Classification of Elements Xth Class Chemistry Notes Part-1

Achievements of Mendeléev’s Periodic Table

                                                          Mendeléev’s Periodic Table contains some gaps but Mendeléev predicted that these gaps are filled by elements discovered in future. And named these undiscovered elements by placing eka (one) as a prefix to the name of preceding element of the same group. For example Gallium discovered later but Mandeleev predict it as Eka-Aluminium.
Properties of Eka-Aluminium and Gallium
Atomic Mass
Formula of Oxide
Formula of Chloride
This prediction of Mandeleev proves correctness and usefulness of Mendeléev’s Periodic Table. Another achievement of Mandeleev is that many scientists now recognize him as originator of the concept on which periodic table is based and also when inert gases (means Nobel gases like He, Ne, Ar) are discovered, they are placed in separate column without disturbing existing order of elements.

Limitation of Mandeleev Classification

                                                These given below are the limitation of Mandeleev Classification. 
1. Position of Hydrogen- No fixed position given to Hydrogen as it behaves like both alkali metals and halogens. Like alkali, Hydrogen react with halogen oxygen and sulphur and also like halogen, Hydrogen exist in diatomic form and react with metals and non-metals. 
2. Isotopes- Isotopes have similar chemical properties but different atomic masses, so Isotopes are challenge to Mandeleev Periodic Law. 
3. Prediction of New Elements- Atomic masses of elements do not increase in regular manner so we cannot predict how many elements can be discovered between two elements.
Modern Periodic Table

                             Henry Moseley in 1913, after performing many experiments proves that atomic number is more fundamental property than atomic mass of an element. So he prepare periodic table on the basis of atomic number means elements are arranged in the order of increasing atomic number in Modern Periodic Table.

Modern Periodic Law

                             According to this law “the properties of elements are the periodic function of their atomic number”.
In Modern Periodic Table limitation of Mandeleev Classification are removed. 

Modern Periodic Table

moseley modern periodic table

Position of Elements in Modern Periodic Table

                                                          Modern Periodic Table contains 18 vertical columns (means 18 Groups) and 7 horizontal rows (means 7 Periods).
In Group- Elements in a group have same number of valence electrons means identical outershell electronic configuration, but as we move downside in a group number of shells increases.
In Period- Elements in a period have same number of shells. Also as we move from left to right in a period, atomic number increases by one unit so number of valence shell electrons also increases by one unit.

Trends in the Modern Periodic Table


          Number of valence electrons in outer most shell of any atom is called valency of that atom. As we move from left to right in a period, atomic number increases by one unit so valence electrons also increases by one unit but in a group it remains constant.

Atomic Size

                   Atomic size is determined by atomic radius.
In a Period- Atomic radius decreases as we move from left to right in a period, because as we move from left to right in a period Nuclear Charge (+ve) increases which pulls electrons (-ve) towards nucleus result in decreasing atomic size or decrease atomic radius.
In a Group- Atomic radius increases as we move from top to bottom in a group, because new shells are added which increases distance between nucleus and outermost electrons.

Metallic and Non-metallic Properties

                                                Elements towards left hand side in periodic table are metals while elements towards right hand side in periodic table are non-metals. Elements which separate metals and non-metals have the properties of the both metals and non-metals are known as Metalloids or Semi-Metals.

Example of Metals- Na, Mg, Al, Fe

Example of Non-metals- S, Cl, F, Br

Examples of Metalloids or Semi-Metals- B, Si, Ge, As, Sb, Te, Po

In a Period- Metallic character decreases and Non-metallic character increases as we move from left to right in a period because tendency to lose valence electrons  decreases due to increasing nuclear charge as we move from left to right in a period.
In a Group- Metallic character increases and Non-metallic character decreases as we move from top to bottom in a group because tendency to lose valence electrons increases due to increasing valence shells (i.e. increasing distance between nucleus and outermost electron) on moving from top to bottom in a group.
Metals are electropositive as they forms bonds by loosing electrons while Nonmetals are electronegative as they forms bonds by gaining electrons.
In general cases, oxides of metals are basic in nature while oxides of non-metals are acidic in nature.

10 Class- Carbon and its Compounds

Carbon and Its Compounds

Allotropes of Carbon - Fulleren-Diamond-Graphite
Allotropes of Carbon - Fulleren-Diamond-Graphite
·             Instead of gaining and loosing electrons, carbon shares its 4-electrons with another element or carbon to form molecule.
·             Covalent bonds are formed as a result of sharing of electrons. Example- H2, O2, N2. Covalent compounds have low melting point and boiling point due to small intermolecular forces.
·             H2 forms by sharing valence electrons (1 per atom of H) and produce single bond between two hydrogen atoms.
·             O2 forms by sharing valence electrons (2 per atom of O) and produce double bond between two oxygen atoms.
·             N2 forms by sharing valence electrons (3 per atom of N) and produce triple bond between two nitrogen atoms.
·             Methane, CH4 is simple carbon compounds and used as a fuel on large scale and also a major component of CNG (Compressed Natural Gas). Methane formed due to sharing of 4 valence electrons of carbon with 4 hydrogen atoms.

Allotropes of Carbon

                                  Carbon have three allotropes i.e. Diamond, Graphite and fullerene.

1.    Diamond:-

                Diamond formed due to rigid three dimensional structures of carbon atoms because each carbon atom bonded to another 4 carbon atoms. It is hardest substance.

2.    Graphite:-

               Graphite formed due to presence of hexagonal array layers above one another, and layers of hexagonal arrays formed because each carbon atom bonded to another 3 carbon atoms with 2 single and 1 double bond. It is smooth, slippery and very good conductor of electricity.

3.    Fullerenes:-

                 Fullerenes (C-60) are also an allotrope of carbon in which carbon atoms are arranged in football like shape.

Versatile Nature of Carbon

                                              Carbon shows versatile nature because it has two characteristics features which are catenation and tetravalency. These both feature gives large numbers of compounds.

1.    Catenation:-

                  Catenation is the property of carbon atom to form bond with other carbon atom to produce large molecule. Catenation produces large long chains, branched chains and ring structures.
Compounds with single bonds are known as saturated compounds while compounds with double or triple bonds are known as unsaturated compounds.

2.    Tetravalency:-

                      Property of carbon atom to form 4 bonds with other atom of carbon or other element is known as tetravalency, as carbon have four valence electrons.

Saturated and Unsaturated Carbon Compounds

1.    Saturated Carbon Compounds:-

                                                 Carbon compounds containing single bond is called saturated Carbon Compounds.
Example- Ethane, C2H6

2.    Unsaturated Carbon Compounds:-

                                                       Carbon compounds containing double or triple bond is called unsaturated Carbon Compounds.
Example- Ethene, C2H4

Chains, Branches and Rings

                                             Carbon is the element which forms chains, branches and rings in its structures.

1.    Chains:-

            Carbons have property to form chains, when one carbon atom attach to another carbon atom like chains.
Example- Ethane(C2H6), Propane(C3H8), Butane(C4H10), Pentane(C5H12), Hexane(C6H14).

2.    Branches:-

               Carbon forms branches when one and two carbon attach to carbon chain.
Example- Butane

3.    Rings:-

          Carbon forms rings when all carbon atoms attach to one another means first carbon chain atom attach to last carbon chain atom giving ring structure.
Example- Cyclohexane(C6H12)

Alkane, Alkene and Alkynes

                                              As we know hydrocarbons are the carbon compounds containing carbon and hydrogen.

1.    Alkane:-

                 Saturated hydrocarbons containing single bonds are known as alkanes.
Example- Ethane (C2H6)

2.    Alkene:-

                 Unsaturated hydrocarbons containing double bonds are known as alkenes.
Example- Ethene (C2H4)

3.    Alkyne:-

                  Unsaturated hydrocarbons containing triple bonds are known as alkynes.
Example- Ethyne (C2H2)

Chemistry of Bonding between Carbon and other atoms

                             Some elements (like halogens, sulpher, oxygen, nitrogen) replace hydrogen from carbon compounds. These elements which replace hydrogen are called as heteroatom.
This heteroatom’s may be present in single or group form and gives specific property to carbon compound and called as functional group. Function group attach to carbon compound by replacing hydrogen atom. 

List of Some Functional Group

Functional Group
Formula of Functional Group
-Cl , -Br, -I
Carboxylic Acid

Homologous Series

                            When same functional group is present on carbon chains of varying length, such series of carbon compounds is known as homologous series.
Example- chemical properties of CH3OH, C2H5OH, C3H7OH and C4H9OH are very similar.

Nomenclature of carbon compounds

                                                          To name any carbon compound just follow below steps-
Step1- Calculate no. of carbon atoms in carbon compound. For example
i.                   If carbon compound have 1 carbon atom then use prefix  Meth
ii.                If carbon compound have 2 carbon atom then use prefix use prefix Eth
iii.             If carbon compound have 3 carbon atom then use prefix Prop
iv.             If carbon compound have 4 carbon atom then use prefix But
v.                If carbon compound have 5 carbon atom then use prefix Pent
vi.             If carbon compound have 6 carbon atom then use prefix Hex
vii.          If carbon compound have 7 carbon atom then use prefix Hept
viii.       If carbon compound have 8 carbon atom then use prefix Oct
ix.             If carbon compound have 9 carbon atom then use prefix Non
x.                If carbon compound have 10 carbon atom then use prefix Dec
xi.             If carbon compound have 11 carbon atom then use prefix Undec
xii.          If carbon compound have 12 carbon atom then use prefix Dodec
xiii.       If carbon compound have 13 carbon atom then use prefix Tridec
xiv.        If carbon compound have 14 carbon atom then use prefix Tetradec
xv.           If carbon compound have 15 carbon atom then use prefix Pentadec
xvi.        If carbon compound have 20 carbon atom then use prefix Eicos
xvii.     If carbon compound have 30 carbon atom then use prefix Triacont
xviii.  If carbon compound have 40 carbon atom then use prefix Tetracont
xix.        If carbon compound have 50 carbon atom then use prefix Pentacont
Example- What is the name of CH4,C2H6 ?
Number of carbon atom in CH4 is 1 so use Meth and it is alkane so use ane so its name is Methane
Number of carbon atom in C2H6 is 2 so use Eth and it is alkane so use ane so its name is Ethane.
Step2- if functional group is present in carbon compound then it is indicated by adding a prefix or a suffix for it as shown in below table-
10th class chemistry notes- Nomenclature of functional groups
Nomenclature of functional groups
Step3- if functional group is a suffix then removes ‘e’ from carbon chain name and add suffix.
Example- Propanone = Propan + One
          ‘Propan’ comes from propane – ‘e’ and, ‘one’ comes from ketone.
Step4- if the carbon compound is unsaturated then ‘ane’ from the name is replaced by ‘ene’ or by ‘yne’ for double or triple bond respectively.
Means ane for single bond, ene for double bond and yne for triple bond.

Chemical Properties of Carbon Compounds

                                                          Carbon compounds show different chemical properties and some of them are study here-

1.    Combustion

Carbon burns in the presence of air (Oxygen i.e. O2) to produce carbon dioxide (CO2), heat and light. This reaction is oxidation reaction.
Saturated hydrocarbon gives clean flame while unsaturated hydrocarbon give yellow flame with too much black smoke.
Example :-
C + O2 --------> CO2 + Heat + Light
CH4 + O2 ------> CO2 + H2O + Heat + Light
CH3CH2OH + O2 --------> CO2 + H2O + Heat + Light

2.    Oxidation

Removal of e- is called oxidation. Burning of fuel or carbon compounds is complete oxidation, but we can also see some incomplete oxidation in chemistry. Oxidizing agents have the ability to add the oxygen to other substances.
CH3CH2OH + {(Alkaline KmnO4 + Heat) or (Acidified K2Cr2O7 + Heat)} ---------> CH3COOH
Acidified Potassium Dichromate or Alkaline Potassium Permanganate is example of oxidizing agents.

3.    Addition Reaction

Addition reaction are the reactions in which hydrogen is added at double bond or triple bonds in unsaturated hydrocarbons in the presence of catalyst like Nickel, Palladium.
R2C=CR2 + H2 + Nickel Catalyst -------> R2CH-CHR2
Example:- Hydrogenation of vegetable oils with Nickel as a catalyst.

4.    Substitution reaction

                                       Substitution reactions are the reactions in which hydrogen atoms is replaced by other elements.
CH4 + Cl2 + Sun Light ------> CH3Cl + HCl

Some Important Carbon Compounds

Ethanol and Ethanoic Acid

                                           Ethanol (C2H5OH) and Ethanoic Acid (CH3COOH) are very valuable carbon compounds.

Ethanol and its Properties:

                                      Ethanol (C2H5OH) is liquid at room temperature with M.P. 156K and B.P. 351K. Ethanol is present in all alcoholic drinks and soluble in water. Ethanol is good solvent so used in many medicines preparations.

Reactions of Ethanol

1.    Reaction with Sodium

When sodium is added to ethanol, it produces sodium ethoxide and hydrogen gas.
2Na + 2C2H5OH ------à 2C2H5O-Na+ (sodium ethoxide) + H2

2.    Reaction to produce unsaturated Hydrocarbon

When we heat ethanol at 443K in the presence of excess concentrated sulphuric acid (H2SO4) produces ethene due to dehydration of ethanol.
CH3CH2OH + Hot Conc. H2SO4 ------à CH2=CH2  + H2O
Conc. Sulphuric acid act as dehydrating agent as it removes water from ethanol.

Question – What is denatured alcohol?

 Answer – ethanol (Alcohol) is used on large scale in industries as solvent so to avoid any misuse of ethanol we add some poisonous substances (like methanol) in it and also add some dyes to provide blue color. This type of alcohol is known as denatured alcohol.

Question – Is alcohol used as Fuel?

Answer – yes, As alcohol (like Ethanol) on burning in sufficient air gives energy, CO2 and H2O

Ethanoic Acid and Its Properties

                                                Ethanoic acid is also known as acetic acid, it belongs to carboxylic acid (weak acids) group. Vinegar is prepared from 5-8% solution of acetic acid in water. Vinegar is used on large scale for the preparation of pickles (Achar). Chemical formula of ethanoic acid is CH3COOH.

Reaction of Ethanoic Acid

1.    Esterification Reaction

Ester is produced, when ethanoic acid get react with the absolute alcohol and acid catalyst is used to catalyse this reaction.
CH3COOH (ethanoic acid) + C2H5OH (ethanol) + acid catalyst --------> CH3COOC2H5 (ester)
Ester gives sweet smells and esters are used for many purposes like in making perfumes, flavoring agents etc.
On treating ester with sodium hydroxide solution (alkali) produces sodium salt of carboxylic acid and alcohol. This reaction is called as saponification reaction as this reaction is used in the preparation of soap.
CH3COOC2H5 + NaOH -----> CH3COONa + C2H5OH

2.    Reaction of Ethanoic Acid with Base

Ethanoic acid reacts with sodium hydroxide (base) to produce water and salt. Sodium  ethanoate also known as sodium acetate.
           CH3COOH + NaOH -----> H2O + CH3COONa

3.    Reaction of Ethanoic Acid with Carbonates

Ethanoic acid and carbonate reacts to produce carbon dioxide, water and salt. This salt is commonly known as sodium acetate.
2CH3COOH + Na2CO3 -------> CO2 + H2O + 2CH3COONa

4.    Reaction of Ethanoic Acid with Hydrogen Carbonates

Ethanoic acid and hydrogen carbonate reacts to produce carbon dioxide, water and salt. This salt is commonly known as sodium acetate.
CH3COOH + NaHCO3 -------> CO2 + H2O + CH3COONa

Soaps and Detergents


          Soap is used for cleaning purpose. As we know, most dirt contains oil, so this dirt does not easily remove and also do not easily dissolve in water.
Soap molecules are potassium or sodium salt of long chain of carboxylic acids. Ionic end of soap is hydrophilic so dissolve in water but long carbon chain is hydrophobic so dissolve in oil. In this way soap molecules form a structure, this structure is named as ‘micelles’.
To form micelle hydrophobic end attach to dirt ( or oil droplet) and hydrophilic end faces outside. This activity creates emulsion in water. These micelles make dirt (or oil droplets) to dissolve in water and at last wash out and as a result we get clothes clean.


                 Detergent is also used for cleaning purpose. Soaps are not very effective in hard water but detergents are very effective in hard water. Detergent molecules are sulphonate or ammonium salts of long chain of carboxylic acids.
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