# The shielding effect and effective nuclear charge

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In summary, nuclear charge refers to the electric charge of a nucleus and is equal to the number of protons in the nucleus times the elementary charge. The effective nuclear charge, on the other hand, takes into account the shielding effect, which is the reduction in the attractive positive charge of nuclear protons on valence electrons. This is due to the balancing of forces of attraction and repulsion between electrons in an atom. The approximation for effective nuclear charge is to subtract the number of core electrons from the number of protons.
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Whats shielding effect and effective nuclear charge?

Per wiki: Nuclear charge is the electric charge of a nucleus of an atom, equal to the number of protons in the nucleus times the elementary charge. In contrast, the effective nuclear charge is the attractive positive charge of nuclear protons acting on valence electrons, which is always less than the total number of protons present in a nucleus due to the shielding effect.[3]

The shielding effect sometimes referred to as atomic shielding or electron shielding describes the attraction between an electron and the nucleus in any atom with more than one electron. The shielding effect can be defined as a reduction in the effective nuclear charge on the electron cloud, due to a difference in the attraction forces on the electrons in the atom.

Every electron in an atom is attracted to every proton in the atom and repelled by every other electron in that atom. Use of the term "shielding" is then somewhat misleading since a shield implies a barrier. In reality what is seen is a balancing of forces of attraction by the forces of repulsion. These forces are vector forces so core electrons (those inner electrons between the valence electrons and the protons in the nucleus) are more effective in balancing than are other valence electrons. The approximation is then to subtract the number of core electrons from the number of protons to determine the effective nuclear charge.

## 1. What is the shielding effect?

The shielding effect refers to the phenomenon in which the inner electrons in an atom shield the outer electrons from the full pull of the positively charged nucleus. This results in a decrease in the effective nuclear charge experienced by the outer electrons.

## 2. How does the shielding effect affect the size of an atom?

The shielding effect plays a significant role in determining the size of an atom. As the inner electrons shield the outer electrons, the effective nuclear charge decreases, causing the outer electrons to be less tightly held by the nucleus. This results in larger atomic radii.

## 3. What is effective nuclear charge?

Effective nuclear charge is the net positive charge experienced by an electron in an atom. It takes into account the shielding effect of the inner electrons, which reduces the full pull of the nucleus on the outer electrons.

## 4. How is the shielding effect related to the periodic trends in the periodic table?

The shielding effect is closely related to the periodic trends in the periodic table. As you move down a group, the number of inner electrons increases, leading to a stronger shielding effect and a decrease in effective nuclear charge. This results in an increase in atomic size and a decrease in ionization energy.

## 5. How does the shielding effect impact the reactivity of elements?

The shielding effect can impact the reactivity of elements by affecting the ease with which outer electrons can be removed or added. As the shielding effect increases, the outer electrons are less tightly held and are more easily lost or gained, leading to increased reactivity.

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