CH 301 Unit 1, Exit Ticket 7 Review: Electron Configurations, Magnetism, and Periodicity Theory

Vocabulary flashcards covering the rules for writing electron configurations of ions, isoelectronic species, paramagnetism vs. diamagnetism, and periodicity theory regarding shielding and effective nuclear charge (ENC).

Electron Configuration of Ions Rule

The rule stating that the number of electrons equals the number of protons, with electrons added or subtracted depending on the charge (for example, the number of $e^-$ for $F^- = 9 + 1 = 10\,e^-$).

Isoelectronic

Sets of ions and atoms that have the identical electron configuration because they all have the same number of electrons (for example, $Ga^{2-}$, $Ge^-$, $As$, $Se^+$, and $Br^{2+}$ all have $33$ electrons and share the configuration $[Ar]\,4s^2\,3d^{10}\,4p^3$).

Paramagnetic

Atoms or ions that contain unpaired electrons; the higher the number of unpaired electrons, the stronger the magnet.

Diamagnetic

Atoms or ions that contain ONLY paired electrons.

Magnetism of Iron ($Fe$)

A $26$-electron system that contains $4$ unpaired electrons, allowing it to act as a strong magnet.

Effective Nuclear Charge (ENC)

The net charge experienced by an electron in an atom, defined by the formula: $\text{ENC} = \text{\# protons} - \text{\# shielding } e^-$.

Periodic Trend of Effective Nuclear Charge (ENC)

On the periodic table, effective nuclear charge increases moving from left to right across a row.

Shielding for $n = 2$ Elements

The amount of core electron shielding experienced by row $n = 2$ elements on the Periodic Table, which equals $2$ shielding electrons (e.g., $Li$ has $3\text{ protons} - 2\text{ shielding } e^- = \text{ENC of } 1$, and $F$ has $9\text{ protons} - 2\text{ shielding } e^- = \text{ENC of } 7$).

Shielding for $n = 3$ Elements

The amount of core electron shielding experienced by row $n = 3$ elements on the Periodic Table, which equals $2 + 8 = 10$ shielding electrons (e.g., for $Al$, $13\text{ protons} - 10\text{ shielding } e^- = \text{ENC of } 3$).

Shell-Dependent Effective Nuclear Charge in Magnesium ($Mg$)

For a magnesium atom ($12$ protons), electrons in the $n = 1$ shell feel an ENC of $12$ (no shielding), electrons in the $n = 2$ shell feel an ENC of $10$ ($2\,e^-$ shielding), and electrons in the $n = 3$ shell feel an ENC of $2$ ($10\,e^-$ shielding).