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Periodic Trends/Patterns. CH. 2. Nuclear charge atomic size or radius ionization energy electron affinity electronegativity metallic character. Reactivity bonding characteristics crystal configurations acidic properties densities. Periodic Trend. Quantum Mechanical Model.
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Periodic Trends/Patterns CH. 2
Nuclear charge atomic size or radius ionization energy electron affinity electronegativity metallic character Reactivity bonding characteristics crystal configurations acidic properties densities Periodic Trend
Quantum Mechanical Model Effective Nuclear Charge:The s, p, d, and f orbitals within a given shell have slightly different energies. The difference in energies between subshells result in electron–electron repulsion whichshieldsouter electrons from the nucleus. The net nuclear charge felt by an electron is called the effective nuclear charge ( Zeff ). Zeff
Quantum Mechanical Model Zeffis lower than actual nuclear charge. Zeff increases toward nucleus ns > np > nd > nf This explains certain periodic changes observed.
Z* The effective nuclear charge in the actual charge from the nucleus that an electron feels due to attractive forces from the nucleus but also repulsive forces from the other electrons, mainly the core electrons.
Periodic Properties 02 Atomic Radii 02:
Ions and Ionic Radii 02 Chapter 06
Trend of ionic radii The cation of an atom decreases in size while the anion of an atom increases in size. The trend can not be made according to the periodic table, but by the isoelectronic series. The more positive an ion is the smaller it is because Zeff increases, while the more negative an ion, the larger it is because Zeff decreases.
Ionization Energy Defined as the amount of energy necessary to remove the outermost electron from an isolated neutral atom in the gaseous state to infinity. Abbreviation is Ei, it has units of kJ/mol. IE
Ionization Energy Minor irregularities in the Ei values are explained by looking at the electron configurations. IE Trend
Ionization Energy Ionization energies vary periodically, which is explained by the changes in Zeff. Zeff
Electron Affinity 01 Electron Energy: Energy change that occurs when an electron is added to an isolated atom in the gaseous state. Abbreviation is Eea, it has units of kJ/mol. Values are generally negative because energy is released. Value of Eea results from interplay of nucleus electron attraction, and electron–electron repulsion. EA
Electron Affinity 02 EA Trend
Metallic Character • The metallic character of atoms can be related to the desire to loose electrons • On the periodic table, the metallic character of the atoms increase down a family and decreases from left to right across a period.
Periodic Trend Activities • WebElements • Periodicity and Properties of Elements and Compounds: An Internet Study • Periodic Trends Lesson • Periodic Table Exercises • Our Favorite Element • Structured Curriculum Lesson Plans