Question

2. Noble gases have zero electron gain enthalpy. Why? -
3.
Which is large in size, Na+ or K. Why? -
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Answer 1

answer is k potassium

noble gases have full octate and does not react

Answer 2

Electron gain enthalpy or electron affinity is the amount of energy released when an electron is added to the valence shell of neutral gaseous atom.

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NOBLE OR INERT gases are the elements in which outermost s, p subshells are completely filled.

They belong to 18 group of periodic table.

They are chemically inactive or unreactive as they have stable configuration. So no chance of combining or reacting with other elements, hence no adding of electrons.

Hence electron gain enthalpy is zero.

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potassium is larger because it has a larger complement of electrons surrounding the nucleus