CHM 101.1

PERIODIC PROPERTIES OF ELEMENTS

  • Elements arranged by increasing atomic number.

  • Trends in chemical, physical, atomic properties predicted by periodic law.

  • Elements achieve stable octet configuration by gaining/losing electrons.

ATOMIC RADIUS

  • Atomic radius: Distance between two nuclei.

  • Types: Covalent radius, ionic radius, metallic radius.

  • Atomic radius decreases across a period (left to right) due to increasing nuclear charge.

  • Atomic radius increases down a group due to more filled electron shells.

CATIONS AND ANIONS

  • Cations (lost electron): Smaller radius than original atom.

  • Anions (gained electron): Larger radius due to decreased effective nuclear charge.

IONIZATION ENERGY (IE)

  • IE: Energy required to remove an electron from a gaseous atom.

  • Increases across a period and decreases down a group.

  • Noble gases have highest IE; elements lower left have lower IE.

ELECTRON AFFINITY (EA)

  • EA: Energy change when adding an electron to a gaseous atom.

  • Generally negative for metals on the right side of the table; noble gases have near-zero EA.

ELECTRONEGATIVITY

  • Measurement of an atom's ability to attract electrons in a bond.

  • Increases from left to right and bottom to top across periodic table.

METALLIC CHARACTER

  • Metals tend to lose electrons (high oxidation potential).

  • Metallic character decreases from left to right and up the periodic table.

TYPES OF BONDING

  • Ionic Bond: Formed by transfer of electrons between electropositive and electronegative elements.

  • Covalent Bond: Formed by sharing electron pairs, occurring between nonmetals.

  • Coordinate Covalent Bond: Formed when one atom donates electron pair.

  • Metallic Bond: Atoms in metals share delocalized electrons, leading to conductivity.

INTERMOLECULAR FORCES

  • Hydrogen Bonding: Strong dipole-dipole interaction with hydrogen bonded to F, N, or O.

  • Dipole-Dipole Interaction: Between molecules with permanent dipoles.

  • Van der Waals Forces: Weak attractive forces between neutral atoms/molecules.