Electron Affinity Trends in 2nd and 3rd Periods

Vocabulary flashcards covering period trends, electron configurations, surface electron density, and electron affinity comparison between 2nd and 3rd period elements.

Order of EA in 3rd Period

The increasing order of electron affinity across 3rd period elements: $Ar < Mg < Al < Na < P < Si < S < Cl$.

2nd Period vs 3rd Period Electron Affinity Anomaly

The trend where 3rd period elements ($Al$, $Si$, $P$, $S$, $Cl$) have a higher electron affinity (more negative \bDelta_{eg}H) than corresponding 2nd period elements ($B$, $C$, $N$, $O$, $F$).

High Surface Electron Density (2nd Period)

A property resulting from the smaller size of $2p$ orbitals ($2p < 3p$) in 2nd period elements, causing greater inter-electronic repulsion for an incoming electron and a less negative \bDelta_{eg}H.

Low Surface Electron Density (3rd Period)

A property resulting from the larger size of $3p$ orbitals in 3rd period elements, causing less repulsion for an incoming electron, greater net attraction, and a more negative \bDelta_{eg}H.

Fluorine Electronic Configuration

[He]\b,2s^2\b,2p^5, a 2nd period element with a small $2p$ orbital causing high surface electron density and less electron affinity than chlorine.

Chlorine Electronic Configuration

[Ne]\b,3s^2\b,3p^5, a 3rd period element with a larger $3p$ orbital causing low surface electron density and higher electron affinity than fluorine.

Electron Gain Enthalpy (Delta_{eg}H)

The enthalpy change associated with adding an electron to a neutral atom, where a more negative value of \bDelta_{eg}H indicates a greater electron affinity (EA).

Silicon vs Phosphorus EA ($p^2 > p^3$)

Silicon ($Si$) has a higher electron affinity than Phosphorus ($P$) because Phosphorus possesses a stable, half-filled $p^3$ electronic configuration.