Chemistry (Part-VII) (Railway)

The tendency of an atom in a molecule to attract the shared pair of electrons towards itself is known as electronegativity.

• In Period 3 of the periodic table, sodium with 11 protons is the least electronegative element (0.93), and chlorine (3.16) with 17 protons is the most electronegative element.

Respiration is the biochemical process in which the cells of an organism obtain energy by combining oxygen and glucose, resulting in the release of carbon dioxide, water, and ATP. It takes place in the mitochondria and requires oxygen and glucose, and produces carbon dioxide, water, and energy.

• The chemical equation is:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (glucose + oxygen → carbon dioxide + water).

Calcium oxide has a high boiling point of 2850°C.

• Sodium Chloride: 1465°C

• Calcium Chloride: 1,935°C

• Lithium Chloride: 1,382°C

On heating, ferrous sulphate crystals lose water and anhydrous ferrous sulphate (FeSO₄) is formed.

• So, their color changes from light green to white.

• On further heating, anhydrous ferrous sulphate decomposes to form ferric oxide (Fe₂O₃), sulphur dioxide (SO₂), and sulphur trioxide (SO₃).

The chemical reaction arrow is one straight arrow pointing from reactant(s) to product(s) and by-products, sometimes along with side products.

• The arrow mark between the products and reactants of a chemical equation shows the direction of the reaction.

• For example, in CuSO₄ + Zn → ZnSO₄ + Cu, the arrow points towards the products ZnSO₄ and Cu.

In 1869, Dmitri Mendeleev came up with a periodic table of chemical elements based on the properties that appeared in the elements.

• The physical property used was the atomic mass of an element.

• The chemical property used was the nature of oxide and hydride formed (i.e., similarity in chemical properties were used by Mendeleev).

Alkynes are organic molecules made of the functional group carbon-carbon triple bonds, with the general formula: CₙH₂ₙ₋₂.

• They are unsaturated hydrocarbons.

• The first member of the alkyne family is CH = CH; Ethyne.

Law of Modern Periodic Table states that properties of elements are the periodic function of their atomic numbers.

• Elements are placed in groups according to their valence electrons and placed in periods according to the number of shells present in them.

• Similarly, in the periodic table, atomic radii decrease from left to right across a row and increase from top to bottom down a column.

2KBr (aq) + BaI₂(aq) → 2KI (aq) + BaBr₂ (s) or Potassium bromide (aq) + Barium iodide (aq) → Potassium iodide (aq) + Barium bromide (s) is a double displacement reaction.

• In the given reaction, the exchange of potassium ion and barium ion takes place simultaneously to form potassium iodide and barium bromide.

The effective nuclear charge is a net positive charge that attracts an electron in an atom.

• Fluorine (F) has the highest effective nuclear charge due to one more proton in its nucleus. Fluorine is highly electronegative element.