Question

storyline 1 exam
36 of 73
which of the following statements about the shielding effect and effective nuclear charge are true? select all that apply.
the actual attraction felt by the electrons farthest from the nucleus is less than the numerical value based on coulombs law
the effective nuclear charge zeff is defined as the net positive nuclear charge that an atoms electron experiences
inner core electrons always shield valence electrons.
the shielding effect describes how the attractive forces between electrons work to increase the amount of attraction each electron feels
valence electrons always shield one another
the shielding effect describes how the repulsive forces between electrons work to reduce the amount of attractive force between electrons

Explanation:

• First statement: According to Coulomb's law \(F = k\frac{q_1q_2}{r^2}\), in an atom, inner - core electrons shield the outer - most electrons from the full nuclear charge. So the actual attraction (which is related to the effective nuclear charge \(Z_{eff}\)) felt by the outermost electrons is less than the attraction calculated using the full nuclear charge (\(Z\)) in Coulomb's law formula.
• Second statement: By definition, the effective nuclear charge \(Z_{eff}\) is the net positive charge that an electron in an atom experiences. It accounts for the shielding of the nucleus by inner - core electrons.
• Third statement: Inner - core electrons are closer to the nucleus and they always shield the valence electrons from the full nuclear charge.
• Fourth statement: The shielding effect is due to the repulsive forces between electrons (not attractive forces). Electrons repel each other, and inner - core electrons repel valence electrons, reducing the net attraction that valence electrons feel towards the nucleus.
• Fifth statement: Valence electrons can shield one another to some extent. For example, in a multi - electron atom with valence electrons in different orbitals (e.g., \(p\) orbitals), the electron - electron repulsions among valence electrons contribute to the shielding.
• Sixth statement: The shielding effect is based on electron - electron repulsions. Inner - core electrons repel valence electrons, which reduces the attractive force that valence electrons would otherwise feel from the nucleus if there were no shielding (i.e., if all electrons were point charges with no repulsion between them).

Answer:

• The actual attraction felt by the electrons farthest from the nucleus is less than the numerical value based on Coulomb's law.
• The effective nuclear charge \(Z_{eff}\) is defined as the net positive nuclear charge that an atom’s electron experiences.
• Inner core electrons always shield valence electrons.
• Valence electrons always shield one another.
• The shielding effect describes how the repulsive forces between electrons work to reduce the amount of attractive force between electrons.