Chemistry MCQs for NEET — Practice Questions with Answers

An element with high electronegativity does not always have high electron affinity. Electronegativity is the tendency of an atom to attract electrons in a chemical bond, while electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase. While there is some correlation, they are not directly proportional, and many exceptions exist.

Basicity of oxides generally increases down the group and from right to left within a period in the periodic table. $K_2O$ (Potassium oxide) is an alkali metal oxide and is highly basic compared to the other given oxides. Alkali metal oxides are strongly basic due to their tendency to dissociate completely in water to form hydroxides.

The element with atomic number 19 is potassium (K), which is an alkali metal. Alkali metals most readily react with halogens to form salts. The element with atomic number 17 is chlorine (Cl), a halogen. Therefore, potassium will most readily react with chlorine.

Electron enthalpy (electron affinity) generally decreases (becomes more negative) across a period and increases (becomes less negative) down a group. Alkali metals, which have low electron affinity, are found at the minima, while noble gases, which have high electron affinity, are found at the maxima.

In a period, from left to right, the metallic character of elements decreases due to an increase in nuclear charge, which attracts electrons more strongly. In a group, from top to bottom, the metallic character increases as the atomic size increases, making it easier for the atoms to lose electrons.

The stability of the lower oxidation state in group 14 elements increases down the group due to the inert pair effect. As we move down the group, the s-electrons are less likely to participate in bonding because they are held more tightly by the nucleus. This effect is known as the inert pair effect.

The correct sequence is TFTT. Statement I is true because ionisation enthalpy is inversely proportional to the shielding effect. Statement II is false because there is no direct relationship between ionisation enthalpy and chemical reactivity. Statement III is true because ionisation enthalpy is inversely proportional to metallic character. Statement IV is true because ionisation enthalpy is directly proportional to effective nuclear charge.