Shielding Effects

This short video depicts electrons in the 1s, 2s and 2p orbitals around a nucleus. The nucleus is composed of positively charged protons. Electrons are attracted to the protons in the nucleus. When 2s electrons are present in the atom, the 1s electrons will shield some of the nuclear charge from the 2s electrons. Generally each electron in an inner shell will shield outer electrons from the equivalent of one proton. When 2p electrons are added the 1s electrons shield a portion of the nuclear charge. In simplest terms 2s electrons do not shield 2p electrons, although Slater Rules describe more accurate shielding effects. We account for the shielding by inner shell electrons when we calculate the effective nuclear charge experienced by an electron in an atom. Z*effective = Z(nuclear charge) - # inner shell electrons.

View the movie depicting the shielding effect in an atom.

The video begins with an energy level diagram showing five shells. Each shell contains subshells and orbitals. As the movie continues the screen will change to show a nucleus with 1s electrons. Next 2s electrons are added. The 2s electrons occupy a larger volume of space compared to the 1s electrons. Since the 1s electrons are closer to the nucleus than the 2s electrons, the 1s electrons shield the 2s electrons from some of the protons positive charge in the nucleus. The 1s electrons also shield some nuclear charge from the 2p electrons.