Chem11 Periodic Trends 2023 PDF

**CHEM11 PERIODIC TRENDS** **Ch. 11** **In general\...** **- The Periodic Table is organized to allow one to\...** 1. **assume certain patterns in the electron configurations of elements.** 2. **see specific patterns related to the organization of the periodic table. a.k.a *[periodic...

**CHEM11 PERIODIC TRENDS** **Ch. 11** **In general\...** **- The Periodic Table is organized to allow one to\...** 1. **assume certain patterns in the electron configurations of elements.** 2. **see specific patterns related to the organization of the periodic table. a.k.a *[periodic trends]*** II. **Atomic and Ionic Radii.** A. **Trends** 1. **Atomic radii decreases from left to right across the periodic table (until group18).** 2. **Atomic and ionic radii increase from top to bottom in a group or family.** **C. Explanations** **a. trend \#1** **- The force of attraction on any orbiting electron increases, resulting in orbitals closer to nucleus** **(a smaller volume).** **b. trend \#2** **- An increase in \# of electrons orbiting the nucleus. Occupy orbitals further from nucleus.** **- The repulsive forces of inner electrons will shield outer valence electrons from attractive** **forces of the nucleus. ak.a. *[Shielding effect]*** **- The repulsive forces also spread out the electron cloud created (3-D volume)** **c. Atomic versus ionic radius** **1. metals and cations** **-lose valence electron(s) from outer orbital. Lower orbitals remain.** **-overall nuclear charge is greater than negative electron charge.** **2. Non-metals & anions** **-gain electron(s) to fill valence/outer orbital.** **-increased neg. charge results in greater mutual electron repulsion.** **-Increases anion radius** III. **Ionization Energy** **-the energy needed to remove an electron from a neutral gaseous atom.** **Element~(g)~ + I. E.\-\-\--\> Ion^+^ ~(g)~ + e^-^** **-many I.E\'s determined in 1920\'s through high-energy electron bombardment** **A. First ionization energy** **- E that bombarding electrons need to eject the most weakly held electron from its nuclei\'s** **influence.** **- elements with low I.E. from positive ions since a small amount of energy is needed to** **remove an electron (ref. Metals)** B. **I.E.\'s and periods** **A. Low I.E.\'s** **e.g. Alkali metals** **- valence electron shielded from nuclei\'s attraction by inner orbitals.** **B. High I.E.\'s** **e.g. Noble gases** **-all valence electrons in full outer orbital of same energy level.** **-nucleus exerts equal influence on all electrons.** **C. Summary** **1. In any period I.E.\'s increase as we move from left to right.** **a. Explanation** **- atomic \# increases, effective nuclear charge increases; so, atomic radii decrease.** **- electrons held more tightly.** **2. I.E.\'s decrease as we go down a family.** **a. Explanation** **-increased atomic number, therefore, greater shielding effect.**