Periodic Trends in Elements

Practice flashcards covering definitions and concepts of periodic properties, atomic radii types, contractions, and ionization enthalpy.

Covalent Radius

One half of the distance between nuclei of two covalently bonded atoms of a non-metallic element joined by a single bond.

Metallic Radius

Taken as half the internuclear distance between metal cores of two adjacent metal atoms in a metallic structure.

Vander-waals Radius

One half of the distance between the nuclei of two adjacent atoms belonging to neighboring molecules of an element in the solid state.

Ionic Radius

The distance between the nucleus of an ion and the point up to which the nucleus exerts its influence on the electron cloud.

Isoelectronic Species

Species containing the same number of electrons, such as $Na^+$, $Mg^{2+}$, and $Al^{3+}$ which all have $10$ electrons.

Lanthanoid Contraction

A regular decrease in atomic radius from lanthanum to lutetium caused by the imperfect shielding of one $4f$ electron by another.

Actinoid Contraction

A general gradual decrease in the size of the atom or $M^{3+}$ ion across the actinoid series due to the poor shielding effect of electrons in the $5f$ orbital.

Transition Contraction

The smaller than expected increase in radius along the $3d$ series due to the poor shielding effect of electrons in the $3d$ orbital.

Ionization Enthalpy

The energy required to remove a closely bound electron from an isolated gaseous atom in its ground state, expressed in units of $kJ\,mol^{-1}$ or $eV\,mol^{-1}$.

Shielding Effect

The reduction in actual nuclear charge felt by valence electrons due to the intervention of filled inner shell orbitals.

Penetration Effect

The proximity of an orbital to the nucleus, following the order $s > p > d > f$, which influences the amount of energy needed to remove an electron.

Enthalpy of Sublimation

The change in enthalpy involved when $1\,mole$ of a solid metal atom changes into metal atoms in a gaseous state.