2-7-1
<h3>Further explanation
</h3>
Electrons can move the shell up or down by releasing energy or absorbing energy
Excited electrons show higher electron transfer to the shell by absorbing energy
So it can be concluded that there are 2 conditions:
Ground state is the state of electrons filling shell with the lowest energy levels.
Excited state is the state of electrons which occupies a higher energy level
The state of excited electrons can be seen from the presence of electrons which do not fill the skin completely but fill the skin afterward
2-7-1
From its 8 electron configuration, filling 3 shells, 2 electrons in the firs shell, 7 electrons in the second shell and 1 electron in the third shell
the electrons in the third shell should fill the electrons in the second shell first according to Aufbau rule (lower energy shells)

D = m / V
0.736 = 225.0 / V
V = 225.0 / 0.736
V = 305.7 cm³
Hello!
The chemical reaction for the dissolving of calcium fluoride is the following:
CaF₂(s) ⇄ Ca⁺²(aq) + 2F⁻(aq)
In this reaction, and according to Le Chatelier's principle, the action that would shift this reaction away from solid calcium fluoride and towards the dissolved ions is the removing of fluoride ions.
Le Chatelier's principle states that in an equilibrium reaction, the system would shift in the opposite direction of the changes. If we remove fluoride ions from the system, it will shift towards the formation of more fluoride ions by dissolving more Calcium Fluoride to achieve equilibrium again.
Have a nice day!
Tt. i’m not fully sure but dominant traits usually always overpower recessive so i’m pretty sure in order for a recessive trait to show both parents need to give the recessive trait in order for it to show. i mean it’s in the words dominant and recessive