What are the trends and exceptions to the trends in electron affinity

Explanation:

Electron affinity is the energy released in adding an electron to a neutral atom in the gas phase.

It is a measure of the readiness of an atom to gain an electron. This property is very peculiar to non-metals. The higher the value, the greater the tendency to accept electrons.

Across a period electron affinity increases due to the increasing nuclear charge not being compensated for.

Down a group, electron affinity decreases  due to the low nuclear charge and the large atomic radii.

The exception to this rule is the stability of half-filled sublevels. For example, nitrogen has a configuration of 2,5 with sublevel notation of 1s²2s²2p³.

The p-sublevel has a degeneracy of three and the three electrons goes in singly. This makes the configuration stable.

We expect such an atom to have a higher electron affinity but its configuration is stable and carbon would have a higher affinity than it across the same period.

Half filled sublevels are exception to the trend of electron affinity.

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm