What is effective nuclear charge?

[adianadiadi]

Exactly what is effective nuclear charge? Is it the ratio of protons to electrons?

[wyzard]

Not exactly the ratio of protons to electrons, the effective nuclear charges refers to the net charge an electron belonging to shell is experiencing from the nucleus, taking account into 'shielding effect', which cancels out some of the positive charge experienced. It is given by the formula: where is the atomic number (number of protons) and is the number of electrons in the inner shell. Here are some examples:

Consider the the carbon atom, its nucleus of the carbon atom contains 6 protons, and it has 2 electron shells with configuration 2,4. The inner shell has an effective nuclear charge of +6 as there are no further inner electrons. The second shell however has an effective nuclear charge of +4, which is 6 - 2, the two electrons from the inner shell cancels out some of the positive charges in the nucleus.

The effective nuclear charge can be used to explain the periodic trend that as you go towards the right of the periodic table, the atoms get more electronegative and it has a stronger tendency to absorb an electron.

[TheAspiringDoc]

Not exactly the ratio of protons to electrons, the effective nuclear charges refers to the net charge an electron belonging to shell is experiencing from the nucleus, taking account into 'shielding effect', which cancels out some of the positive charge experienced. It is given by the formula: where is the atomic number (number of protons) and is the number of electrons in the inner shell. Here are some examples:

Consider the the carbon atom, its nucleus of the carbon atom contains 6 protons, and it has 2 electron shells with configuration 2,4. The inner shell has an effective nuclear charge of +6 as there are no further inner electrons. The second shell however has an effective nuclear charge of +4, which is 6 - 2, the two electrons from the inner shell cancels out some of the positive charges in the nucleus.

The effective nuclear charge can be used to explain the periodic trend that as you go towards the right of the periodic table, the atoms get more electronegative and it has a stronger tendency to absorb an electron.

I thought it was all but the valence shell..?
 

[wyzard]

I thought it was all but the valence shell..?
 

I think it's mainly used for studying the effective nuclear charge experienced by the electrons of the valence shell as that's where the chemical behavior of the atom is exhibited.

I've included effective nuclear charge experienced by the electron in the intermediate shells, for example the second shell of calcium atom, which has 4 shells. In wikipedia (https://en.wikipedia.org/wiki/Effective_nuclear_charge) is "the average number of electrons between the nucleus and the electron in question", so it can be the valence electron, or the inner electrons.