Carbon - Introduction & General Properties PDF

## Carbon ### Introduction - Symbol: C - Atomic mass: 12 amu - Atomic number: 6 - Nature of element: Non-metal - Group: IVA - Block: p-block - Electronic configuration: 1s², 2s² 2p² - Valency: 4 - Melting point: 3800 K - Isotopes: ⁶C¹², ⁶C¹³, ⁶C¹⁴ ### General Properties of the Carbon Family - Car...

## Carbon ### Introduction - Symbol: C - Atomic mass: 12 amu - Atomic number: 6 - Nature of element: Non-metal - Group: IVA - Block: p-block - Electronic configuration: 1s², 2s² 2p² - Valency: 4 - Melting point: 3800 K - Isotopes: ⁶C¹², ⁶C¹³, ⁶C¹⁴ ### General Properties of the Carbon Family - Carbon family: Consists of carbon, silicon, germanium, tin, and lead. - Electronic configuration: They have four electrons in their outermost orbit (ns², np²) and are p-block elements. - Carbon: [He] 2s² 2p² - Silicon: [Ne] 3s² 3p² - Germanium: [Ar] 3d¹⁰ 4s² 4p² - Tin: [Kr] 4d¹⁰ 5s² 5p² - Lead: [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p² - Atomic radius: It increases down the group with an increase in atomic number. - Metallic character: Metallic character increases as the atomic number increases. - Carbon (C) and Silicon (Si) are non-metals. However, Silicon shows characteristics of semi-metal. - Germanium is a metalloid (properties of metal and non-metal). Tin and lead are metals. - Melting and boiling points: Their melting and boiling points decrease down the group. - Allotropy: Except lead other elements show allotropy. - For example, carbon exists in crystalline (diamond, graphite, graphene, fullerene, carbon nanotube) and amorphous allotropes (coke, coal, charcoal, carbon black, lampblack, gas carbon etc). - Silicon has various allotropic forms. Germanium has two crystalline forms. - Tin exists as white tin and grey tin. - Valency: Carbon cannot exceed covalency greater than four because it has no vacant d-orbitals. But silicon and others can show valency of more than four due to the presence of d-orbitals in their atoms. ### Occurrence - Carbon occurs in both a native and combined state in nature. - In a free state (native), it occurs in the form of coal, graphite, and diamond. - In a combined state, it occurs in living tissues, natural gas, petroleum, and coal deposits. - It occurs as CO₂ in the air. - It also occurs as carbonate in rocks and minerals like chalk, limestone, marble, dolomite, etc. ### Allotropes of Carbon - Carbon exhibits different allotropic modifications. - If an element exists in two or more forms that are physically different but chemically identical in properties, this phenomenon is called allotropy and such forms are called allotropes or allotropic modifications. - The various allotropic forms of carbon are broadly classified as: - Crystalline form - Amorphous form - The allotropic forms having certain geometrical shapes and sizes are called crystalline forms. - Similarly, the allotropic forms which are smooth and do not possess geometrical shape and size are called amorphous forms. They exist in powder form. ### Proof of Allotropy - All allotropes of carbon contain the same element of carbon. - To prove this, equal weights (say 1g) of different allotropes like diamond and graphite are heated at different temperatures separately in different vessels in excess supply of air. - The evolved CO₂ gas from different allotropes is passed into weighed KOH bulb separately provided that no leakage of CO₂. - This gas is absorbed completely by weighed KOH bulb and the weight of the KOH bulb is noted. - Experimentally, in each case, the increase in weight due to the mass of CO₂ remains constant. - Thus, the equal weight of the different allotropes yields the same weight of carbon dioxide when burnt in oxygen. - C + O₂ → CO₂ - CO₂ + 2KOH → K₂CO₃ + H₂O - This experiment proves that all allotropes consist of the same element carbon. ### Crystalline Allotropes of Carbon - Diamond - Properties - Diamond is the hardest crystalline allotrope of carbon. - It is the purest form of carbon (100% carbon). - Its pure form is colorless and transparent to X-ray.