Question

Which orbital has the highest energy and why $?$

Answer 1

An orbital is a mathematical function that describes the location and the wave-like behaviour of an electron in an atom. An orbital may also be called an atomic orbital or electron orbital. There are four types of orbitals named for their energy sublevels. They are $s,p,d,$ and $f$ orbitals. Each orbital type has a unique shape based on the energy of its electrons. The energy subshells are arranged by principal energy levels.

Complete answer:
The principal energy level of an electron refers to the orbital in which the electron is located relative to the atom's nucleus. This level is denoted by the principal quantum number $n$. If the number of principal energy levels associated with an orbital is increased then the energy of the orbital is increased. For example, the energy of $2s$ orbital will be greater than $1s$ orbital.
Then within a given principal energy level, the energy of the electrons in the $p$ orbital will be more energetic than the electrons in the $s$ orbital. The energy of the electrons in the $d$orbital will be more than the $p$ orbital. Similarly, the energy of the $f$ orbital will be more than the $d$ orbital.

Additional information: The first principal energy level has one sublevel that contains one $s$ orbital. The $s$ orbital can contain a maximum of $2$ electrons. The next principal energy level contains one $s$ orbital and three $p$ orbitals. The set of three $p$ orbitals can hold up to $6$ electrons.

Note:
Note that an orbital can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus. There are many types of atomic orbital ( $s,p,d,f,g,h,...$), but only the first four are occupied in the ground state of an atom. The energy of an electron is the energy it would require to rip it out of the atom’s electron cloud.