Science - Classification of Elements (PDF)

# Classification of Elements * There are pure and impure matters around us. * They are in the form of elements, compounds, and mixtures. * Till now 118 elements have been discovered so far. * 92 are natural and 26 are artificial. ## Questions to Think About * **Are all elements made up of the same...

# Classification of Elements * There are pure and impure matters around us. * They are in the form of elements, compounds, and mixtures. * Till now 118 elements have been discovered so far. * 92 are natural and 26 are artificial. ## Questions to Think About * **Are all elements made up of the same type of atoms?** * **Are the physical and chemical properties of one element similar to that of another element?** * **How has this made the study of elements easier?** * **What is the classification of elements?** * **Why are the elements classified?** * **What is the basis of classification of elements?** ## Activity 14.1 **Classify the elements used in our daily life as metals and non-metals:** | Element | Metal | Non Metal | |---|---|---| | Oxygen | | X | | Iron | X | | | Silver | X | | | Sodium | X | | | Chlorine | | X | | Aluminum | X | | | Carbon | | X | | Sulfur | | X | | Nitrogen | | X | ## Questions and Observations * **Do all metals have the same properties?** * **Is there any relation between the atomic structure of elements and the similarity or differences between the properties of elements?** * **How are the properties of elements related to the atomic structures?** ## Periodic Table **The scientific table made for the study of elements by keeping elements of similar properties in the same group and elements of different properties in different groups is called a periodic table.** * Russian scientist Dmitri Mendeleev had created a periodic table for the classification of elements on the basis of their atomic weight. * Mendeleev formulated a periodic law for the classification of elements on the basis of his study. * The law is known as Mendeleev's Periodic law. * "The physical and chemical properties of elements are the periodic functions of their atomic weight." * It means that when the elements are arranged according to the increasing order of their atomic weights then their physical and chemical properties recur periodically. * Elements with similar properties lie in the same vertical column and the elements with different properties in between them lie in a horizontal row. * This way, a classification table for elements is made which is known as a periodic table. * The vertical columns of a periodic table are called groups and the horizontal rows are called periods. ## Modern Periodic Table * Mendeleev had considered atomic weight of elements as their fundamental property. * Many complexities were seen in the periodic table when elements were classified on the basis of atomic weight. * Some elements have more than one atomic weight. * For example: C-12, C-13, and C-14 are isotopes of carbon. * Their atomic weights are 12, 13 and 14 respectively. * The forms of the same element having different atomic weights are called isotopes. * The number of protons in an atom is always constant whereas the number of neutrons may differ thus forming the isotopes. * Mendeleev's periodic table was made on the basis of the atomic weight so separate spaces should be given for the isotopes of the same elements. * He only allocated one space for an element and did not give separate spaces for their isotopes. * His periodic law could not explain some other properties of the elements. * Scientists went on to prove that atomic weight is not the fundamental properties of elements and kept searching for a new law for the periodic table. ## Henry Moseley and the Periodic Table * English scientist Henry Moseley in 1913 AD discovered that the properties of elements depend on atomic number rather than on atomic weight. * He formulated modern periodic law on this basis. * The modern periodic law can be stated as, "the physical and chemical properties of elements are the periodic function of their atomic number." * Moseley made a new periodic table on the basis of his periodic law. * It is known as the modern periodic table or long form of periodic table. * The elements have been arranged in the increasing order of their atomic number. * Elements with similar properties are kept in the same vertical column which is known as a group. * Elements with the increasing order of their atomic number are kept in horizontal row which is known as period. # Electronic Configuration of Elements Based on Sub Shells * The path in which electrons revolve around the nucleus of an atom is called orbit or shell. * A shell may be divided into one or more subshells. * There are one or more orbitals in a subshell. * Electrons are found in these orbitals. * All the properties of elements could not be explained using the electronic configuration of elements based on shells. * Scientists developed the electronic configuration of elements based on the subshells through their research. * There are 1, 2, 3 and 4 subshells in K, L, M and N shells respectively. * The subshell in K shell is denoted as 1s. * 2s and 2p are the subshells of L shell, 3s, 3p, and 3d are the subshells of M shell. * 4s, 4p, 4d, and 4f are the subshells of N shell. * s, p, d, and f subshells can accommodate a maximum of 2, 6, 10, and 14 electrons respectively. ## Example | Subshell | Shell | Subshell | Total electrons in shell | |---|---|---|---| | 1 | K | _1s²_ | 2 | | 2 | L | _2s², 2p⁶_ | 8 | | 3 | M | _2s², 2p⁶, 3d¹⁰_ | 18 | | 4 | N | _4s², 4p⁶, 4d¹⁰, 4f¹⁴_ | 32 | ## Activity 14.2 * Study the modern periodic table. * Prepare the periodic table in cardboard paper or chart paper. * Keep separate colors for the groups and discuss the prepared table. ## Activity 14.3 * Prepare a periodic table. * Arrange the elements from atomic number 1 to 20. * Show the alkali metals, alkaline earth metals, halogens and inert gases with different colors. | | IA | IIA | IIIA | IVA | VA | VIA | VIIA | 0 | |---|---|---|---|---|---|---|---|---| | 1 | H | | | | | | | He | | 2 | Li | Be | B | C | N | O | F | NE | | 3 | Na | Mg | Al | Si | P | S | Cl | Ar | | 4 | K | Ca | | | | | | | | 5 | | | | | | | | | # Electronic Configuration of Elements Based on Sub Shells * The electronic configuration of elements on the basis of subshells is guided by Aufbau's principle. * Aufbau's principle states that electrons are filled in a subshell in the increasing order of energy of these subshells. * The increasing order of energy of subshells or electrons are filled in subshells in the following order: * n = 1 _1s_ * n = 2 _2s_ _2p_ * n = 3 _3s_ _3p_ _3d_ * n = 4 _4s_ _4p_ _4d_ _4f_ * n = 5 _5s_ _5p_ _5d_ _5f_ * n = 6 _6s_ _6p_ * n = 7 _7s_ * n = 8 _8s_ * The order of subshells according to their increasing energies is: _1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p ..._ * The maximum number of electrons which s, p, d, and f subshell can accommodate are 2, 6, 10, and 14. * Electrons could not be filled in 2s subshell till 1s subshell is not completely filled. * Electrons should be filled serially in the order: _1s, 2s2p, 3s 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p ..._ ## Activity 14.4 **Complete the table:** | shell | subshell | Maximum number of electrons accommodated in subshell | maximum number of electrons in the shell | |---|---|---|---| | K | _1s_ | 2 | 2 | | L | _2s_ | 2 | 8 | | | _2p_ | 6 | | | M | _3s_ | 2 | 18 | | | _3p_ | 6 | | | | _3d_ | 10 | | | N | _4s_ | 2 | 32 | | | _4p_ | 6 | | | | _4d_ | 10 | | | | _4f_ | 14 | | **Explain the relationship between electronic configuration based on shell and subshell.** # Classification of Elements in Modern Periodic Table **The elements are classified in the modern periodic table on the basis of their properties.** * The elements are arranged in the increasing order of their atomic number in the modern periodic table. * There are 7 periods and 18 groups. | Period | Number of Elements | Nature of Period | |---|---|---| | First | 2 | Very short | | Second | 8 | Short | | Third | 8 | Short | | Fourth | 18 | Long | | Fifth | 18 | Long | | Sixth | 32 | Very Long | | Seventh | 32 | Very Long | **Modern periodic table has been divided into 18 groups according to the IUPAC system.** ## Activity 14.5 1. **Write the electronic configuration of hydrogen, alkali metal, and halogen.** 2. **Write the similarities between the electronic configurations of hydrogen, halogen, and alkali metals.** 3. **What are the differences between the electronic configurations of hydrogen, halogens and alkali metals?** 4. **Which group of the periodic table is suitable for hydrogen? Discuss and draw a logical conclusion.** # Metals, Nonmetals and Metalloids * Elements are classified into three groups i.e., metals, nonmetals, and metalloids on the basis of their metallic characters. ## Metal * Metals are placed on the left side of the modern periodic table. * All the elements of group IA to IIIA (except boron) are metals. * The metals of group IIA and IIIA are less reactive than the metals of group IA. * The elements of group IIIB to IIB are less reactive transitional metals. * For example: Fe, Co, Ni, Ag, Au, Hg, Zn etc.. * Their properties lie between the active metals and nonmetals so they are also known as transitional metals. * Metals are good conductors of heat and electricity. * **The elements having one electron in their outermost shell lie in group IA.** * Elements like Li, Na, and K lie in this group. * These are reactive metals. * They form a strong base or alkali when dissolved in water so they are also known as alkali metals. * Their valence shell electronic configuration is _ns¹_. Here 'n' denotes the shell. * For example, the electronic configuration of sodium is _1s², 2s² 2p, 3s₁_. * The elements of this group are soft and have less density. * **The elements having two electrons in their outermost shell lie in group IIA.** * The elements like Mg and Ca lie in this group. * Their valence shell electronic configuration is _ns²_. * For example, the electronic configuration of magnesium is _1s², 2s² 2p⁶ 3s²_. * The elements of this group are known as alkaline earth metals because the oxides of these metals are soluble in water and they are found on the earth's surface. ## Non-Metal * Nonmetals are kept on the right side of the periodic table. * The elements of VA, VIA and VIIA along with elements of group VIIIA or 18 (0) are non-metals. * **The elements having seven electrons in their valence shell are kept in group VIIA (17) of the modern periodic table.** * Elements like F, Cl, Br, I lie in this group. * They easily take part in reaction to gain one electron from others to fulfill their valence shell with eight electrons. * They are very reactive. * The outermost electronic configuration of these elements is _ns²np⁵_. * For example, the electronic configuration of chlorine is _1s², 2s² 2p, 3s² 3p⁵_. * The elements of this group (F, Cl, Br, I) are called halogens. * They are soft and have less density and are the most reactive nonmetals. * **The elements having eight electrons in their valence shell and two electrons in their first shell which is also their valence shell are kept in group 0.** * The elements like He, Ne, Ar, Kr, Xe and Rn are in this group. * Their valence shell electronic configuration is _ns² np⁶_. * For example, the electronic configuration of Argon is _1s², 2s² 2p⁶, 3s² 3p⁶_. * These elements are also known as noble gases or inert gases . * Since they have a complete octet in their valence shell, they do not take part in chemical reactions so they are known as inert gases. ## Metalloid * The elements which lie between metals and nonmetals in the periodic table and show some properties similar to metals and some properties similar to nonmetals are called metalloids. * They are poor/semiconductors of electricity. * Their electrical conductivity is less than metals and more than nonmetals. * Silicon (Si), Germanium (Ge), Bismuth (Bi) etc. are metalloids. ## Activity 14.6 * Study the modern periodic table. * Fill the elements from atomic number 1 to 20 in groups IA to 0. * Use different coloured inks for filling the names of metals, nonmetals and metalloids. * Demonstrate the model of your periodic table in your classroom. # Characteristics of Period and Group in Periodic Table * The properties of elements depend on the group and period of that element in the periodic table. * It is due to this fact that the periodic table is important to study the properties of the elements. * Periods and groups have their own properties in the periodic table. ## A. Valency * The outermost shell of an atom is called its valence shell. * The electron present in the valence shell of an atom is called valence electron. * There is change in the electronic configuration of elements as we move from left to right in a period. * Although the number of shells is the same in a period, the number of valence electrons goes on increasing due to which the valency of elements changes. * So the valencies of elements in a period as we move from group IA to VIIA and group 0, are 1, 2, 3, 4, 3, 2, 1, and 0 respectively. * **The valency of an element is determined by the number of valence electrons.** * All the elements of a group have the same valency. * The valency of elements of group IA and VIIA is 1 and that of elements of group IIA and VIA is 2. * Similarly, the elements of group IIIA and VA have their valency 3 generally. ## Activity 14. 7 * Write the elements of group IA and 3rd period in vertical column and horizontal row respectively as in the periodic table and write their electronic configuration. * Write similarities and differences in their properties on the basis of their number of shells and valencies. * What changes are seen in the valencies as we move from top to bottom of a group and left to right of a period in the periodic table? Draw a conclusion. ## A. Atomic Size * The atomic size of elements decreases from left to right of a period. * The number of protons and electrons increases with the increase in atomic number while the number of shells remains the same. * The increased electrons are filled in the same shell. * Similarly, due to the increase in the number of protons, the positive charge of the nucleus also increases and the electrons in the shell are attracted with more force. * As a result, the atom gets contracted. * So, the size of atoms is decreased from group1 to 18 in a period. * **Atomic size is determined by the distance of the valence shell from the nucleus of that atom.** * For example, Lithium atoms have K and L shells whereas sodium atoms have K, L, and M shells. * So, the size of the sodium atom is more than the size of the Lithium atom in group IA. ## Activity 14.8 1. **Draw the atomic structure of Li, Be, B, N, and C.** 2. **Arrange these elements in the increasing order of their atomic size.** 3. **Draw the atomic structure of K, Li, and Na.** 4. **Arrange these elements in the increasing order of their atomic size.** 5. **What are the changes in atomic size as we move from left to right in a period and top to bottom in a group? Draw conclusions from it.** ## C. Electropositivity and Electronegativity * The property of an element to lose its valence electrons and form positive ions (cations) is called electropositivity * The property of an element to gain electrons in its valence shell to form negative ions (anions) is called electronegativity. * The atomic size of elements decreases from left to right of any period so their electron losing capacity decreases along the period whereas their capacity to gain electrons increases accordingly. * Due to this, the electropositivity or metallic character of elements decreases from group 1 to 18 of any period whereas their electronegativity or nonmetallic character increases. * **As we move from top to bottom of a group, the tendency of elements to lose electrons increases due to the increment in their atomic size.** * So, their electropositivity character also increases. * But their capacity to gain electrons decreases due to the increase in distance from the nucleus. * Hence, electronegativity decreases down a group. ## Activity 14.9 1. **Write the electronic configuration of Na, Mg, Al, Si, P, S, and Cl.** 2. **Arrange these elements in the increasing order of their electronegativity.** 3. **Similarly arrange them in the increasing order of their electropositivity.** 4. **Write the electronic configuration of Be, Mg, and Ca.** 5. **Arrange them in the increasing order of their electropositivity.** * Draw conclusions from this activity by observing and studying the periodic table also and present it in the class. ## D. Chemical Reactivity * The chemical reactivity of metals decreases along a period whereas the chemical reactivity of nonmetals increases along a period. * But the element in the extreme right of a period is inert. | Atomic Number | Element | Number of Valence Electrons | Valency | |---|---|---|---| | 11 | Na | 1 | 1 | | 12 | Mg | 2 | 2 | | 13 | Al | 3 | 3 | | 14 | Si | 4 | 4 | | 15 | P | 5 | 3 | | 16 | S | 6 | 2 | | 17 | Cl | 7 | 1 | | 18 | Ar | 8 | 0 | * As you can see, the atomic number increases from left to right in the third period. * The number of protons and electrons also increases accordingly while the same number of shells is the same. * The electrons go on adding in the same shell * The number of protons also increases inside the nucleus due to which the attraction force of the nucleus also increases. * Hence, the electrons in the shell are attracted more towards the nucleus. * Thus, sodium has the largest size among the elements given above. * Sodium is the most electropositive or the most reactive metal in the third period. * Argon is the smallest among them but it is an inert gas so chlorine is the most electronegative or most reactive nonmetal among them. * **The chemical reactivity of metals increases from top to bottom of a group whereas the reactivity of non-metals decreases..** * The size of elements increases down a group due to which they can easily lose their valence electrons so the reactivity of metals increases. * For example, the reactivity of group IIA elements increases in the order of Be < Mg < Ca. * The tendency of nonmetals to gain electrons decreases when their size increases. * So, the chemical reactivity of nonmetals decreases down a group. * For example, the reactivity order of nonmetals of group VIA is O > S > Se. ## Project Work 1. **Make the atomic models of Lithium, Sodium and Potassium using clay or paper or any other suitable materials.** * Make the size of sodium larger than that of lithium and size of potassium larger than that of sodium. * Observe these atomic models and discuss the properties of group IA of the periodic table. 2. **Make the atomic models of elements of the second period like Lithium, Beryllium, Boron, Carbon, etc.using clay or paper or any other suitable materials. Discuss the properties of the second period on the basis of these models and present in the classroom.** # Exercise 1. **Choose the correct option for the following questions.** a. Which is the main ore of iron? * i. Bauxite * ii. Argentite * iii. Hematite * iv.Pyrite b. Which metal is found in pure state in nature? * i. Aluminium * ii. Iron * iii. Copper * iv. Gold c. Which is the primary step of purifying metal? * i. Smelting * ii. Roasting * iii. Concentration * iv. Grinding d. Which of the following ore is oxidised by roasting method? * i. Hematite * ii. Siderite * iii. Bauxite * iv. Cuprite e. In which process is smelting included? * i. Grinding * ii. Refining * iii. Oxidation * iv. Reduction 2. **Give reason:** a. All ores are minerals but all minerals are not ores. b. Ores are oxidised after concentration. 3. **Write the differences between:** a. Mineral and ore b. Roasting and calcination c. Oxidation and reduction 4. **Answer the following questions:** a. What are the sources of metals? b. Make a list of ores of iron, copper, aluminium, and silver. c. How is metallurgy a stepwise process? Explain. d. How pure metals are obtained from electro-refining? Explain it with an activity. e. Explain the difference between contact, internal, and systemic pesticides. f. What are the uses of ammonia? g. Explain the advantages and disadvantages of using pesticides. h. Write any four uses of methane gas. i. What is detergent? Write its two examples. What effects are seen on the human health and environment due to the use of detergent? Present your argument. j. There has been an excessive use of chemical pesticides in Hari's village due to which complex problems have been observed in the health of people and the environment. What may be the alternatives to solve these problems? Give some suggestions. k. What do you mean by chemical pollution? What are its effects? Write practical ways to minimize it. l. Write about the pollution caused by industrial products like cement, glass, ceramics, plastic, fiber, chemical fertilizers, soap, detergent, etc. in your locality. Write its causes and suggest proper ways for management. m. Explain the soap making process. # Hydrocarbons and its Compounds * There are different types of compounds around us. * These compounds can be classified as carbonic and non-carbonic or organic and inorganic. * The compounds obtained from minerals are called non-carbonic compounds or inorganic compounds. * The compounds obtained from plant and animal sources are called carbonic compounds or organic compounds. * All the compounds of carbon except its oxides, carbonates, bicarbonates, and carbides are the organic compounds. * The carbonic compounds composed of only carbon and hydrogen are called hydrocarbons. ## Hydrocarbon **Collect locally available materials like wood pieces, sugar, stone, water, cooking oil, ghee, rice, maize, glass, iron pieces, etc.** * **Make fire using the wood pieces in an open place.** * **Then put the above materials in the fire one by one and observe.** * **Classify the objects which burn in fire and which do not burn and fill the given table.** | S.N. | Name of the object | Combustible | Non combustible | |---|---|---|---| | 1 | Wood | X | | | 2 | Sugar | | X | | 3 | Stone | | X | | 4 | Water | | X | | 5 | Cooking Oil | X | | | 6 | Ghee | X | | | 7 | Rice | X | | | 8 | Maize | X | | | 9 | Glass | | X | | 10 | Iron Pieces | | X | ## Conclusion * **On this basis, all combustible substances are organic and non-combustible substances are inorganic.** <start_of_image> Our daily life is filled with several examples of hydrocarbons: * **All combustible substances consist of carbon and hydrogen.** * **Hydrocarbons are made of carbon and hydrogen.** * * **Kerosene lamps are lit in the villages where there is no hydroelectricity.** * * **Firewood is used to cook food.** * * **Spirit lamps are used in laboratories as a source of heat.** * * **Charcoal is used to heat and melt metals while making utensils.** * **All of these combustible substances contain carbon and hydrogen.** * **These substances are obtained from plants and animals.** * **The substances which are obtained from plants and animals and are combustible are called organic compounds.** * **Organic compounds found in the human body like protein, hormone, carbohydrate, fat, enzyme, protoplasm, etc. all are organic compounds.** # Organic Compounds * **Generally, the compounds of carbon covalently bonded to other carbon atoms or hydrogen atoms are called organic compounds.** * **Besides hydrogen, the carbon may also form covalent bonds with other elements like oxygen, nitrogen, halogens, sulphur, and phosphorus.** * **CO2, CO, HCO3-, CO- are not organic compounds although they contain carbon atoms.** * **Generally organic compounds are composed of elements like carbon, hydrogen, oxygen, nitrogen, halogen, sulphur, and phosphorus.** * **Some organic compounds may also contain metal bonded to them** Examples of organic compounds include: * **methane, ethane, ethene, acetylene, methanol, chloroform, urea, insulin, protein, oil, etc.** * **The branch of chemistry which deals with the study of these compounds is called carbonic chemistry or organic chemistry.** * **Petroleum is the main source of hydrocarbons.** * **The hydrocarbons are classified as saturated and unsaturated on the basis of types of bonds between the carbon atoms.** ## Activity 18.2 * **Make a model of a hydrocarbon molecule.** * **Materials required: clay dough or flour dough, color, matchstick or toothpick.** * **Method/Procedure:** 1. Make some spherical shapes from the clay or flour dough of different sizes. 2. Paint bigger spherical shapes red and assume them to be carbon atoms and paint smaller spherical shapes white and assume them to be hydrogen atoms. 3. Then prepare a model of hydrocarbon as shown in the figure. * Now, have a discussion in your classroom. ## Saturated Hydrocarbon * **The hydrocarbons having a single covalent bond between the carbon atoms are called saturated hydrocarbons.** * They are very stable and less reactive so they are known as paraffin. * **They are also called alkanes.** * **The general formula of these compounds is C₂H₂n +2 where 'n' is the number of carbon atoms.** * **Here n = 1, 2, 3, 4............** | Name | Molecular Formula | Condensed Formula | Structural Formula | |---|---|---|---| | Methane | CH4 | CH4 | H H-C-H H | | Ethane | C2H6 | H3CCH3 | | Propane | C3H8 | H3CCH2CH3 | | Butane | C4H1o | HC(CH3)2CH3 | | Pentane | C5H12 | HC(CH3)2CH3 | ## Unsaturated Hydrocarbon * **The hydrocarbons having double or triple covalent bond between the carbon atoms are called unsaturated hydrocarbons.** * They are less stable and are very reactive so they are known as olefins. * **They are also known as alkene and alkyne.** ## Alkene * The hydrocarbons having a double covalent bond between the carbons atoms are called alkene. * **Example: ethene, propene, butene, etc.** * **The general formula of these compounds is CnH2n-2 where 'n' is the number of carbon atoms.** | Name | Molecular Formula | Condensed Formula | Structural Formula | |---|---|---|---| | Ethene | C2H4 | H2C=CH2 | H H C = C H H | | Propene | C3H6 | H3C-CH=CH2 | | Butene | C4H8 | H2C-CH2-CH=CH2 | ## Alkyne * The hydrocarbons having a triple covalent bond between the carbon atoms are called alkyne. * **Example: ethyne, propyne, butyne, etc.** * **The general formula of these compounds is CnH2n-2 where 'n' is the number of carbon atoms.** | Name | Molecular Formula | Condensed Formula | Structural Formula | |---|---|---|---| | Ethyne | C2H2 | HC≡CH | H-C≡C-H | | Propyne | C3H4 | HC≡C-CH | | Butyne | C4H6 | HC≡C-CH2-CH | * **The process of making Vanaspati ghee from vegetable oil is called hydrogenation.** * **In hydrogenation, the unsaturated fatty acids change to saturated fatty acids.** * **H2C=CH2 + H2 → C2H6** ## Differences Between Saturated and Unsaturated Hydrocarbons | Saturated Hydrocarbon | Unsaturated Hydrocarbon | |---|---| | The Hydrocarbon having a single covalent bond between the carbon atoms is called saturated hydrocarbon. | The Hydrocarbon having double or triple covalent bond between the carbon atoms is called unsaturated hydrocarbon. | | Saturated hydrocarbons are stable. | Unsaturated hydrocarbons are unstable or they are chemically reactive. | | They are also known as alkane (CH2n+2). For example, CH4, C2H6, C3H8 | They are also known as alkene (CH2n) and alkyne (CH2n-2). For example, C2H4, C2H2, C3H4 | ## Homologous Series * **The series of hydrocarbons which can be represented by the same general formula is called a homologous series.** * **Each member of this series is called a homologue.** * **All the members of the series can be represented by a common formula and the adjacent homologue of the series differs by CH2 group.** * **Similarly, the molecular weight of adjacent members of the series or homologue differs by 14.** | Name | Molecular Formula | |---|---| | Methanol | CH3OH | | Ethanol | CH3CH2OH | | Propanol | CH3CH2CH2OH | ## Alkyl Radical * **The group of atoms formed by removing one hydrogen atom from an alkane molecule is called an alkyl radical.** * **It can be represented by a general formula CH2n+1. ** * **For example -CH3+, -CH2CH3+, etc.** * **For example: CH3+, CH2CH3+** ## Functional Group * An atom or a group of atoms which determines * the structure and chemical reactivity of a certain group of organic compounds is called a functional group.* * **The functional groups get attached to the alkyl groups to form different groups of organic compounds.** * **Example of functional groups -O-, -CHO, -COOH** # Nomenclature of Hydrocarbons * **IUPAC means International Union of Pure and Applied Chemistry.** * **It is a system established by scientists to make uniformity in the names of organic and inorganic compounds all over the world.** * **According to this system, a compound has the same or only one name.** * **This removes the mistake while naming or understanding the compounds.** ## Common System of Nomenclature of Hydrocarbons 1. **Find the word root on the basis of number of carbon atoms as:** | No of carbon atoms | Word Root | Notation | |---|---|---| | C-1 | Meth | C1 | | C-2 | Eth | C2 | | C-3 | Prop | C3 | | C-4 | But | C4 | | C-5 | Pent | C5 | | C-6 | Hex | C6 | | C-7 | Hept | C7 | | C-8 | Oct | C8 | | C-9 | Non | C9 | | C-10 | Dec | C10 | 2. **In this way after finding the word root, add the suffixes like ane, ene and yne according to the number of bonds between the carbon atoms.** * **For example:** * **CH3-CH3** * There are two carbon atoms so the word root is *eth* and there is only one covalent bond between the carbon atoms, so we should add *ane* as the suffix. * So, its name is *eth+ane* = *ethane* ## Some Important Hydrocarbons and Their Compounds ### Methane * **This gas is found in marshy places so it is also known as marsh gas.** * **Its molecular formula is CH4.** * **This gas is generally found above the minerals oil.** * **It is also found in gobar gas or bio gas, and sewage gases.** * **It is colourless, odourless, and tasteless.** * **It is not soluble in water but soluble in organic solvents like ether, alcohol, etc** **Uses of methane:** 1. **Methane is used for cooking food as gobar gas or biogas and as a fuel in industries.** 2. **It is used to prepare carbon black which is used to make printing ink, shoe polish and paint.** 3. **Methane is also used to prepare chloroform, carbon tetrachloride, methyl alcohol, formaldehyde, etc.** 4. **It is also used in the industrial preparation of hydrogen gas.** ### Ethane * **Ethane is a saturated hydrocarbon having two carbon atoms bonded with a single covalent bond.** * **Its molecular formula is C2H6.** * **It is found along with methane gas in natural gas,煤气, and petroleum mines.** * **It is also colourless, odourless, and tasteless as methane.** * **It is also insoluble in water but soluble in organic solvents like ether, alcohol, etc.** **Uses of ethane:** 1. **It produces heat on combustion so it is used in metal welding.** 2. **It is also used to prepare carbonic compounds like ethyl chloride, nitro ethane, etc.** ### Propane *