Direction (Q. Nos. 11-15) This section contains 5 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONE or MORE THAN ONE are correct.Q.Which of the following property do not increase down the group from oxygen to polonium?a)Atomic sizeb)Densityc)Electron affinityd)Ionisation energyCorrect answer is option 'C,D'. Can you explain this answer?

Question

Answer

Atomic Size:
- The atomic size generally increases down a group from oxygen to polonium.
- This is because as we move down the group, an extra shell of electrons is added to the atom, leading to an increase in atomic size.
- The increase in atomic size is due to the increase in the number of energy levels or shells.

Density:
- The density generally increases down a group from oxygen to polonium.
- This is because as we move down the group, the atomic mass of the elements increases due to the addition of more protons, neutrons, and electrons.
- The increase in atomic mass leads to an increase in the packing of atoms in a given volume, resulting in an increase in density.

Electron Affinity:
- The electron affinity generally decreases down a group from oxygen to polonium.
- Electron affinity is the energy change that occurs when an atom gains an electron to form a negative ion.
- As we move down the group, the atomic size increases, and the effective nuclear charge experienced by the outermost electrons decreases.
- This makes it easier for the atom to accept an additional electron, resulting in a decrease in electron affinity.

Ionisation Energy:
- The ionisation energy generally decreases down a group from oxygen to polonium.
- Ionisation energy is the energy required to remove an electron from an atom, forming a positive ion.
- As we move down the group, the atomic size increases, and the effective nuclear charge experienced by the outermost electrons decreases.
- This makes it easier to remove an electron from the atom, resulting in a decrease in ionisation energy.

Conclusion:
- Based on the given options, the properties that do not increase down the group from oxygen to polonium are electron affinity and ionisation energy.
- Both electron affinity and ionisation energy decrease down the group as explained above.

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