CHE2B Lecture Notes: Periodic Properties and Atomic Structure

Vocabulary flashcards covering atomic properties, electron removal order, magnetic behavior, effective nuclear charge, atomic and ionic size trends, ionization energies, and electron affinity.

Metal Ion Electron Removal Order

To form metal ions, electrons are removed first from the outermost $p$ orbitals, followed by the $s$ orbital, and finally the $d$ orbitals.

Diamagnetic Atoms and Ions

Atoms and ions that have all electrons paired and are weakly repelled by a magnetic field.

Paramagnetic Atoms and Ions

Atoms and ions that have unpaired electrons and are attracted to an external magnetic field.

Atomic Radius

A measure of atomic size defined as half the distance between the nuclei in a homonuclear molecule.

Effective Nuclear Charge ($Z_{eff}$)

The effective positive charge experienced by valence electrons, calculated as $Z_{eff} = Z - S$, where $Z$ is the atomic number and $S$ is the number of core electrons.

Cation Radius Trend

Cations are smaller than their corresponding neutral atoms because having fewer electrons leads to weaker electron-electron repulsion, holding the remaining electrons more tightly.

Anion Radius Trend

Anions are larger than their neutral atoms because having more electrons leads to stronger electron-electron repulsion, holding the electrons more loosely.

Isoelectronic Ions

Ions that share the same electron configuration (such as $1s^2 2s^2 2p^6$); for these ions, a greater atomic number ($Z$) yields a smaller ionic radius.

Ionization Energy

The minimum energy required to remove the highest energy electron from a gaseous atom or ion, which is always positive as work is done against particle attraction.

First Ionization Energy ($I_1$)

The energy required to remove the first electron from a gaseous atom, represented by $Mg(g) \rightarrow Mg^+(g) + e^-$ with $I_1 = 738\,kJ\,mol^{-1}$.

Second Ionization Energy ($I_2$)

The energy required to remove an electron from a singly charged gaseous cation, represented by $Mg^+(g) \rightarrow Mg^{2+}(g) + e^-$ with $I_2 = 1451\,kJ\,mol^{-1}$, which is always larger than the first ionization energy.

Electron Affinity ($EA$)

The energy change associated with adding an electron to a gaseous atom to form an anion, such as $X(g) + e^- \rightarrow X^-(g)$, which can be positive or negative.