Railway Science (Chemistry-Miscellaneous)

Ionic compound - the compound formed by the oppositely charged ions which attract each other to form a chemical bond. Examples - CaCI₂ , NaCI, CaO. Identification of ionic compounds - Elements in the compound are metal and non-metal, the naming of the compound is done as the name of metal will be in the first place while non-metal will be second. Bonding takes place between these groups (groups 1, 2 or 3 and groups 5, 6, or 7 ).

Compounds that consist of ions are known as ionic atoms. Atoms that gain or lose electrons are called ions, ions may have a negative charge or positive charge. Ionic bonds are generally between metals and non-metals.
Properties of ionic compounds - high boiling and melting points, formation of crystals, conduct electricity, higher enthalpies of fusion and vaporization, require a lot of energy to break etc.

Melting point - Point at which a substance changes its state from solid to liquid. Factors affecting the melting point:- Hydrogen bonding, Impurity, Pressure, etc. Melting point of some compounds - Aluminium chloride (AlCl₃) - 192.6 ℃, Aluminium oxide (Al₂O₃) - 2053 ℃, Barium (Ba) - 727 ℃, Barium sulfate (BaSO₄) - 1580 ℃, Hydrogen chloride (HCl) - (-114.17 ℃), Nitric acid (HNO₃) - (-41.6 ℃), Lithium chloride (LiCl) - 610 ℃, Mercury (Hg) - (-38.8 ℃), Nitrogen (N₂) - (-210 ℃), Oxygen (O₂) - (-218.79 ℃), Ozone (O₃) - (-193 ℃).

Covalent bond - A chemical bond that involves the sharing of electrons to form electron pairs between atoms. Properties of Covalent Bond: do not conduct electricity, are generally not soluble in water, have strong chemical bonds that exist between atoms, have low melting and boiling points, etc. Examples - Hydrogen (H₂), oxygen (O₂), nitrogen (N₂), water (H₂O), methane (CH₄), etc.

Covalent bond consists of the mutual sharing of one or more pairs of electrons between two atoms. Sharing of electrons between atoms of the same element, for example, formation of H₂ , Cl₂ , O₂ , etc.
Sharing of electrons between atoms of different elements, for example, formation of CH₄ , H₂O, NH₃ , etc.

Nitrogen has 5 valence electrons therefore needs three more electrons to complete its octet configuration. Mutual sharing of three pairs of electrons gives a triple covalent bond. Structure N ☰ N three bonds exist between Nitrogen atoms. Nitrogen (N) is a p-block element belonging to Group 15.

An Ionic bond is the bond formed by the complete transfer of valence electrons so as to attain stability. Examples of Ionic Bonds NaCl (Sodium chloride), NaF (Sodium fluoride). Ionic compounds typically are solids at room temperature.

Ionization of water : Water is a weak electrolyte that undergoes only little self ionization. The ionic product of water is the product of the concentrations of H+ and OHions in water at a given temperature.
Water Atomization Process refers to a process that sprays and collides water at a high pressure of about 50-150 Mega Pascal against a molten metal melted at a high temperature to produce fine metal powder (atomized powder) at the micron level.
Hydrolysis is any chemical reaction in which a molecule of water breaks one or more chemical bonds.

Sublimation - The change of a substance from solid to straight gas state (For Example - dry ice is a frozen form of carbon dioxide).
The process of a liquid becoming a gas is called boiling (or evaporation) (For Example- salt is prepared naturally by evaporation of seawater), while the process of a gas becoming a liquid is called condensation (For Example - water that forms on the outside of a cold cup).
Deposition is the phase transition in which gas transforms into solid without passing through the liquid phase (For Example - when water vapor changes directly to ice).