At a certain temperature, the ph of a neutral solution is 7.61. what is the value of kw at that temperature?

A neutral solution means we are having equal amount of H⁺ and OH⁻. As we know,
                               Kw  =  [H⁺] [OH⁻]      (1)

So, in order to calculate Kw we first need to calculate [H⁺] and [OH⁻],

As,                        pH  =  -log [H⁺]
Or,
                             [H⁺]  =  10⁻ˣ                  ∴ x = pH = 7.61

Putting value, and solving

                             [H⁺]  =  2.45 × 10⁻⁸

As, our system is neutral, so concentration of [OH⁻] is exactly equal to concentration of [H⁺]. Now, putting values of [H⁺] and [OH⁻] in equation 1.

                               Kw  =  [2.45 × 10⁻⁸] [2.45 × 10⁻⁸]

                               Kw  =  6.00 × 10⁻¹⁶

They carry out the exchange of gases as we breathe ( oxygen and carbon dioxide).

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.