Nuclear Charge

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1. How do you find effective nuclear charge?

Nuclear charge values have been determined for the elements. These values are recorded in encyclopedias, scientific textbooks, and scientific journal articles.  

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2. How do you calculate effective nuclear charge?

You can calculate effective nuclear charge if you know the number of inner electrons and the number of protons of an atom, both which can be found either from the periodic table or from online resources. The equation for calculating nuclear charge is Zeff = Z - S, where Zeff  is the effective nuclear charge, Z is the number of protons, and S is the number of inner electrons. 

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3. What is the nuclear charge of an atom?

Nuclear charge is a measure of the ability of protons in the nucleus to attract the negative electrons in orbit around the nucleus. Electrons are attracted to the nucleus as it is positively charged, but electrons in the inner shells can negate some of the attraction of the nucleus on the outermost electrons. The net attraction on these outer electrons is known as effective nuclear charge.

The nucleus of an atom contains positively charged particles called protons. Electrons are attracted to the nucleus as they are negatively charged. However, negatively charged electrons around the nucleus are organized into layers called orbitals which repel each other, and negate some of the positive charge of the nucleus. This results in a varying attraction of the nucleus on the electrons surrounding the nucleus, which is known as nuclear charge. The presence of electrons on the inner shells of an atom “shield” the outermost electron from feeling the full positive charge. Because of the varying charge on electrons in different orbitals, we typically refer to the effective nuclear charge, which is the effect of the nucleus experienced by the outermost electron of the atom, taking into account the shielding effect of inner electrons. 

We can calculate the effective nuclear charge by subtracting the number of inner shell electrons from the number of protons.

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The force exerted on an outer electron by the nucleus can be determined by measuring the charge of the nucleus, the charge of the electron, and the radius between the nucleus and outermost electrons. We can then use those numbers with Coloumb’s law to calculate the effective force of the nucleus on an electron. By multiplying the Coloumb’s law constant k (9.0 x 109 N × m2 / C2)  by q1, the effective nuclear charge, and q2, the charge of the electron, and dividing by the radius of the atom squared we can find F, which is the force of attraction between the nucleus and the outer electron.

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Knowing the effective nuclear charge allows us to determine how much energy is required to remove one electron, also known as ionizing the atom. Ionization energy is an important concept for reactivity of the elements. 

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Electron Configuration and Structure

Shielding of the Nucleus

Ionisation Energies

Shielding (Expert)

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