Question

Consider the addition of an electron to the following atoms from the fourth period. Rank the atoms in order from the most negative to the least negative electron affinity values based on their electron configurations.

Br, Ge, Kr

Answer 1

The order of the atoms from highest to lowest electron affinity values based on their electron configurations is Br, Kr, and Ge.

Step-by-step explanation:

The order of the atoms from highest to lowest electron affinity values based on their electron configurations is: Br > Kr > Ge.

While Br, Kr, and Ge are all atoms from the fourth period, their electron affinities can be determined by considering their positions in the periodic table and the trends in electron affinity.

Br, which belongs to Group 17, has the highest electron affinity because it needs only one more electron to achieve a stable electron configuration. Kr has a lower electron affinity than Br because it is a noble gas and already has a stable electron configuration. Ge, which belongs to Group 14, has the lowest electron affinity among the three because it would need to gain four electrons to achieve a stable electron configuration.

Answer 2

Electron configurations:

Ge: [Ar] 3d10 4s2 4p2 => 6 electrons in the outer shell

Br: [Ar] 3d10 4s2 4p5 => 7 electrons in the outer shell

Kr: [Ar] 3d10 4s2 4p6 => 8 electrons in the outer shell

The electron affinity or propension to attract electrons is given by the electronic configuration. Remember that the most stable configuration is that were the last shell is full, i.e. it has 8 electrons.

The closer an atom is to reach the 8 electrons in the outer shell the bigger the electron affinity.

Of the three elements, Br needs only 1 electron to have 8 electrons in the outer shell, so it has the biggest electron affinity (the least negative).

Ge: needs 2 electrons to have 8 electrons in the outer shell, so it has a smaller (more negative) electron affinity than Br.

Kr, which is a noble gas, has 8 electrons and is not willing to attract more electrons at all, the it has the lowest (more negative) electron affinity of all three to the extension that really the ion is so unstable that it does not make sense to talk about a number for the electron affinity of this atom.