Railway Science (Chemistry-Structure of Atom)

It is the smallest unit into which matter can be divided without the release of electrically charged particles. Electrons are negatively charged subatomic particles that orbit the nucleus of an atom. Molecule - Two or more atoms held together by chemical bonds. An ion is an atom or molecule that has gained or lost one or more electrons and has a net electrical charge.

It is an element with Atomic number - 17. Belongs to the group of halogens i.e 17th group of periodic table. Compound - A substance that is composed of two or more different elements chemically bonded together in a fixed ratio. Water (H₂O) is composed of hydrogen and oxygen atoms. Ammonia (NH₃) - Composed of Nitrogen and Hydrogen atoms. Nitrogen peroxide, Composed of nitrogen and oxygen atoms.

The bond that is formed by sharing two-electron pairs. Example - Oxygen (O₂), Carbon Dioxide (CO₂), Sulfur Dioxide, Nitrogen Dioxide (NO₂), Ozone (O₃), Ethylene (C₂H₄). Triple covalent bond : The bond that is formed by sharing three electron pairs. Example - Cyanide (CN⁻), Ethyne (C₂H₂), Nitrogen (N₂). Electrovalent bonds - When electrons are transferred from atoms of one element to atoms of another element, producing positive and negative ions.

Here, Sodium, Magnesium and Aluminum ions all have the same electronic configuration. So, on increasing the number of protons without increasing the number of electrons, that extra positive charge pulls in the electron tighter giving a smaller radius. So the smallest will be Al ³⁺ and largest will be Na⁺ .

The Chemical formula for washing soda is Na₂CO₃ .10H₂O also known as Sodium Carbonate decahydrate. This indicates that each molecule of washing soda contains 2 sodium atoms (Na), 1 carbon atom (C), and 3 oxygen atoms (O) and 10 water molecules (H₂O) per molecule.

Copper sulfate exists in different forms, including hydrates where water molecules are associated with the copper sulfate molecules. The most common form is copper sulfate pentahydrate (CuSO₄ ⋅5H₂O), which contains 5 water molecules per molecule of Copper sulfate. Another name for Copper sulfate is Blue Vitriol.

It belongs to group 17 of the modern periodic table thus having 7 electrons in the last orbits. When Chlorine atoms share one electron pair between each other, they get a stable octet. Non-Polar Covalent Bond - It forms between two same atoms. Examples - Oxygen (O₂), nitrogen (N₂) and ozone (O₃). Polar Covalent Bond - It forms between two different atoms. Examples - Sulphuric acid (H₂SO₄), Water (H₂O), Ammonia molecule (NH₃).

This refers to the average distance between the nucleus of an atom and its outermost shell of electrons. On the periodic table, atomic radius generally decreases as we move from left to right across a period (due to increasing nuclear charge) and increases as we move down a group (due to the increasing number of electron shells).

Molarity: This refers to the concentration of a solution, expressed as the number of moles of solute per liter of solution. Normality: This is another concentration unit based on the number of equivalents per liter of solution.

An electron, symbolized as "e", is a negatively charged particle with a mass at rest approximately equal to 9.11 × 10⁻³¹ kilograms, denoted as "mₑ".