Question

The bromine atom possesses 35 electrons. It contains 6 electrons in 2p orbital, 6 electrons in 3p orbital and 5 electrons in 4p orbital. Which of these electrons experiences the lowest effective nuclear charge?

Answer 1

Hint: The effective nuclear charge is directly affected by the distance between the nucleus and electrons in the orbitals of the atom which we consider. Thus the orbital which is farthest from the nucleus will experience the lowest effective nuclear charge among 2p, 3p and 4p orbitals.

Complete step by step answer:
-Let’s start with the concept of effective nuclear charge .It can be defined as the attraction of the protons present inside the nucleus of an atom to the outermost electrons.

- When we move across the period in a periodic table, the successive electrons are being added to the orbitals in the same shell and as we can see, the shielding of the nuclear charge by the core electrons do not vary to a great amount to decrease the attraction of electrons to the nucleus. Thus, we can say that the effective nuclear charge is more dominant than the screening effect.

- When we move down a group in a periodic table, the outermost electron becomes further away from the nucleus and as a result, the shielding effect increases by the core electrons. Thus, we can say that the screening effect is more dominant than nuclear charge if we consider a group.

- In short, as we go away from the nucleus, the effective nuclear charge goes on decreasing. Among the given orbitals, 4p orbitals are the orbitals which are farthest from the nucleus of the bromine atom. As a result the 4p electrons will experience the lowest effective nuclear charge.

- Also the 4p electrons are being shielded by the electrons in 2p and 3p orbitals along with the electrons in s orbital. Thus the electrons in 4p orbital will experience the lowest effective nuclear charge among 2p, 3p and 4p electrons.

Note: Keep in mind that, as the principal quantum number increases (n), the effective nuclear charge will decrease and the screening effect increases. Also, the electrons in the same principal shell are not much effective at shielding one another from the nuclear charge, whereas the electrons filled in the inner shells are greatly effective at shielding electrons in outer shells from the nuclear charge.