Question

Consider the n = 3 energy level in a hydrogen atom. how many electrons can be placed in this level?

Answer 1

18 electrons

Step-by-step explanation:

There can be up to 2 electrons in 1 orbital.

In the level 3, there are 3 sublevels: 3s, 3p and 3d.

• The sublevel 3s has 1 orbital 3s, thus, 1 × 2 e⁻ = 2 e⁻.
• The sublevel 3p has 3 orbitals 3p, thus, 3 × 2 e⁻ = 6 e⁻.
• The sublevel 3d has 5 orbitals 3d, thus 5 × 2 e⁻ = 10 e⁻.

The total number of electrons is 2 + 6 + 10 = 18 e⁻.

Alternatively, we can find the number of electrons in a level using the formula:

2n² = 2 × 3² = 2 × 9 = 18 electrons

Answer 2

According to Neils Bohr, the atomic structure is described as electrons orbiting around the nucleus in orbitals. Each orbital holds two electrons that are oppositely spinning, according to Pauli's Exclusion Principle. These orbitals are then located in sub-shells of varying energy levels. There are 4 types of these sub-shells. In order of decreasing energy, they are the s, p ,d and f sub-shells. They differ in shape and energy levels. The s sub-shell holds 1 orbital, p holds 3, d holds 5 and f holds 7 orbitals. These sub-shells are oriented according to their principal quantum number, n. There are a total of 7 energy levels with 1 being the strongest and closest to the nucleus, and 14 being the weakest and farthest to the nucleus. You will see that electrons are filled from the strongest 1s orbitals, to the weakest 7f orbital.

Thus, in the energy level n=3, there are 3s, 3p, 3d and 3f sub-shells. The total electrons for this energy level is. therefore,

Total electrons = 1(2) + 3(2) + 5(2) + 7(2) = 32 electrons

The 2rd energy level can hold up to 16 orbitals containing two electron each. That would be 32 electrons all in all.