Question

Effective nuclear charge \(\left(Z_{\text {eff }}\right)\) for a nucleus of an atom is defined as (a) shielding of the outermost shell electrons from the nucleus by the innermost shell electrons (b) the net positive charge experienced by electron from the nucleus (c) the attractive force experienced by the nucleus from electron (d) screening of positive charge on nucleus by innermost shell electrons.

Short answer

The correct definition of effective nuclear charge (\( Z_{\text{eff}} \) ) is (b) the net positive charge experienced by electron from the nucleus.

Step-by-step solution

Understanding Effective Nuclear Charge

Effective nuclear charge (\( Z_{\text{eff}} \) ) is the net positive charge experienced by an electron in an atom. This concept takes into account the fact that electrons in the outer shells are partially shielded from the full charge of the nucleus by the electrons in the inner shells. The closer an electron is to the nucleus, the more it feels the nucleus's full positive charge; the farther away it is, the more the inner electrons shield it, effectively reducing the charge it experiences from the nucleus.

Analyze the Options

To determine which definition correctly defines effective nuclear charge, we must compare the given options with the concept explained in the previous step. (a) and (d) refer to the shielding effect, but they do not mention the net positive charge experienced by outermost electrons. (c) is incorrect because it discusses the force experienced by the nucleus, not the electron. Therefore, (b) is the most accurate definition of effective nuclear charge as it directly refers to the net positive charge felt by an electron due to the nucleus.

Key concepts

Shielding Effect

The shielding effect is an important concept in understanding how electrons behave within an atom. It describes how inner shell electrons can interfere with the attraction between the nucleus and the electrons in the outermost shell. Imagine the nucleus of an atom playing tug-of-war with the electrons. Those closer to the core have a strong grip, while outer electrons feel a weaker pull. That’s because the inner teammates are in the way, blocking part of the overall force.

Electrons are negatively charged and they repel each other. Because of this repulsion, electrons in these inner shells provide a sort of 'shield.' This makes the effective attraction of the nucleus for the outer electrons less than it would be if these inner electrons weren't there. It's like a crowd between you and a magnet; the closer you are to the magnet, the stronger you'll feel its pull.

Atomic Structure

When we delve into the atomic structure, we are basically investigating the architecture of atoms. At the very heart is the nucleus, a dense core that houses protons and neutrons. Surrounding this central hub are the electrons, arranged in layers known as electron shells or energy levels. Each shell can only hold a certain number of electrons, and filling these shells obey a specific order, always starting from the one closest to the nucleus.

The atomic structure influences everything from the element's chemical properties to its place on the periodic table. Electrons within inner shells are like the foundation of a building, creating the base upon which the stability of outer electrons is determined. The balance between the positive charge of the nucleus and the negative charge of electrons is crucial, making sure the atom does not collapse or fly apart.

Electron-Nucleus Interaction

Electron-nucleus interaction refers to the attraction between the positively charged nucleus and negatively charged electrons. This is the force that essentially keeps the atom together. The strength of this interaction can vary significantly due to the shielding effect. Since the nucleus contains protons, it has a positive charge that lures the negative electrons. This tug-of-war creates an 'orbital' path for the electrons around the nucleus.

In simple terms, this interaction is a lot like gravity between Earth and the Moon, keeping the electrons in orbit around the nucleus just as gravity keeps the Moon circling Earth. However, not all electrons feel this pull equally. Those in the inner orbitals are like front-row spectators at a concert, experiencing every note up close. In contrast, electrons in the outer orbitals, much like people in the back rows, receive a muffled experience due to the shielding by the 'fans' in front of them.