Is 2s or 2p closer to the nucleus?

Because it is less effectively shielded, a 2s electron experiences a higher effective nuclear charge and is held closer to the nucleus than a 2p electron which gives the 2s orbital a lower energy.
A.

What is the difference between 1s and 2s?

2s orbital has more energy than 1s orbital. Also 2s orbital has a nodal plane but 1s orbital doesn't have any nodes. They are in different shells. Both orbitals have the same spherical shape as indicated by the “s”.
• Why are the 2s and 2p orbitals degenerate in hydrogen?

Multi-electron atoms. When an atom only contains a single electron, its orbital energies depend only on the principle quantum numbers: a 2s orbital would be degenerate with a 2p orbital. s-orbitals tend to be closer to the nucleus than p-orbitals and don't get as much shielding, and hence become lower in energy.
• Why do electrons go into the 4s orbital before the 3d?

We say that the 4s orbitals have a lower energy than the 3d, and so the 4s orbitals are filled first. We know that the 4s electrons are lost first during ionization. The electrons lost first will come from the highest energy level, furthest from the influence of the nucleus.
• How many orbitals are contained in the 2p sublevel?

There can be two electrons in one orbital maximum. The s sublevel has just one orbital, so can contain 2 electrons max. The p sublevel has 3 orbitals, so can contain 6 electrons max. The d sublevel has 5 orbitals, so can contain 10 electrons max.
B.

Why is the energy of the 2s orbital lower than the energy of a 2p orbital Why is the energy of the 2s orbital lower than the energy of a 2p orbital?

The higher effective nuclear charge experienced by the 2s electrons in carbon (as a result of the closer penetration in to the nucleus) compared with the 2p electrons in carbon means that the 2s electrons experience a stronger attraction to the nucleus and therefore possess lower orbital energy than the 2p electrons.
• Why is the 4s orbital lower in energy than 3d?

We say that the 4s orbitals have a lower energy than the 3d, and so the 4s orbitals are filled first. We know that the 4s electrons are lost first during ionization. The electrons lost first will come from the highest energy level, furthest from the influence of the nucleus.
• How many nodes are in the 3d orbital?

You will have observed that the total number of nodes is equal to the principal quantum number, n, minus one. In other words, the 1s has 0 nodes the 2s and the 2p orbitals each have 1 node the 3s, 3p and 3d orbitals each have 2 nodes the 4s, 4p, 4d, and 4f orbitals each have 3 nodes and so on.
• What is meant by radial node?

Radial node is a spherical surface where the probability of finding an electron is zero. The number of radial nodes increase with principle quantum number (n). Angular node is also called nodal plane. Angular node is a plane that passing through the nucleus. Angular node is equal to the azimuthal quantum number (l).

Updated: 2nd October 2019