Railway Science (Chemistry-Periodic Table) (Part-III)

Valence electrons: The electrons in the outermost shell of an atom; On moving down the group, there is no change in the number of valence electrons as the valency of all the elements present in the same group is the same. F, Br and Cl belong to Group 17 (Halogens group), Boron (B, Group 13), Carbon (C, Group 14), Nitrogen (N, Group 15), Hydrogen (H, Group 1), Helium (He, group 18).

Uses - vulcanisation of black rubber, production of sulfuric acid, as a fungicide and in black gunpowder. Silicon (Si): atomic number -14, valency - 4. Phosphorus (P): atomic number - 15, valency - 3 or 5.

Zinc (Zn): Atomic number - 30, Block - d-block. Uses - to galvanise other metals such as iron to prevent rusting, and to help the immune system and metabolism function in the body. Position of other elements: Group 11, Period 4 - Copper (Cu). 3rd period, 15th group - Phosphorus (P).

The atomic number of Al is 13. Thus, it contains 13 protons and 13 electrons. The electronic configuration of Al is 2,8,3. The outermost shell of an atom is called the valence shell, and the electrons in that shell are called the valence electrons. Ca, and Mg both have 2 valence electrons and Nitrogen (N) has 5 valence electrons.

Carbon compounds are present everywhere, for example in food, in cloth and in lead of pencil. The atomic number is 6 and the atomic mass is 12.01g mol⁻¹ . Allotropes of Carbon: Diamond, graphite, Graphene, and Buckminsterfullerene.
Carbon Compounds: Ethanol and Ethanoic Acid. Chemical Properties: Combustion, Oxidative Addition Reaction and Substitution Reaction. Uses: in the synthesis of many dyes and drugs, Diamond is used for cutting marble, granite and glass, it is also used for jewellery and Graphite is used to make electrodes for electrolytic cells, for making pencils, lubricants for machines.

Argon (Ar) is a noble gas (Atomic number 18 , Mass 39.948 g.mol-1) discovered by Sir Ramsay and Lord Rayleigh in 1894. It is the third most abundant gas in earth’s atmosphere.
Properties: It is odorless, colourless gas. It is characterized by the same solubility level in water as that of oxygen. It has low thermal conductivity. Uses: In metal industries and in the production of titanium.

Fe (Iron): Group - 8, Period - 4, Atomic number - 26. D - block elements - The elements that can be found from the third group to the twelfth group of the modern periodic table.
The valance electrons of these elements fall under d - orbit. It is also referred to as transition elements or transition metals.
Calcium (Ca): Group - 2, Period - 4, Atomic number - 20. Magnesium (Mg): Group - 2, Period - 3, Atomic number - 12. Sodium (Na): Group - 1, Period - 3, Atomic number - 11.

The second-lightest of the halogens. It is a yellow-green gas at room temperature. It is a p-block element. Atomic number - 17, Electronic configuration - 1s²2s²2p⁶3s²3p⁵ .
The valence electrons - 7. Hydrogen (H): Atomic number (1), Electronic configuration (1s¹). Helium (He): Atomic number (2), Electronic configuration (1s²). Carbon (C): Atomic Number (6), Electronic configuration (1s²2s²2p² ).

Each element has a one or two-letter symbol, which is an abbreviated form of its present or former name. Symbols of some elements are formed from the first letter of the name and a letter, appearing later in the name. Examples: chlorine (Cl), zinc (Zn) etc.
Other symbols have been taken from the names of elements in Latin, German or Greek. For example, Fe (Iron) - ferrum (Latin), Na (Sodium) - natrium (Latin), K (potassium) - kalium.

Other elements and their symbols : Zn - Zinc (Atomic number - 30), Fe - Iron (Atomic number - 26), Mg - Magnesium (Atomic number - 12), Na - Sodium (Atomic number - 11), Al - Aluminium (Atomic number - 13), S - Sulphur (Atomic number -16).