CHEMISTRY · Single correct · AP · Chemistry · Atomic Structure and Properties · Atomic Structure and Properties
Problem
Across a single period, the graph of first-ionization energy generally rises from left to right but displays a noticeable local minimum at the element with Z=13. Which explanation best accounts for this dip in the otherwise increasing trend?
(a) Removal of the electron leaves the 3p subshell half-filled, a particularly stable arrangement, so less energy is needed to ionize the Z=13 atom.
(b) The 3p electron removed from the Z=13 atom experiences greater shielding than a 3s electron, lowering the energy required to ionize the atom.
(c) The atomic radius of the Z=13 element is larger than that of the preceding element, and the greater distance between the outer electron and the nucleus lowers the ionization energy.
(d) Because the first electron removed from the Z=13 atom is a 3s electron, and 3s electrons are farther from the nucleus than 3p electrons in the same shell, less energy is necessary for ionization.