Ch08 Periodic Trends Exploring electron configurations and...

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Periodic Trends Exploring electron configurations and the properties they produce. Ch08 © Nick DeMello, PhD. 2007-2016 version 1.5
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Exploring Trends in Electronic Structure Atomic Radius Non-Bonding Radius vs Bonding Radius Trends Across Periodic Table Down Periodic Table Transition Metals Magnetism Ions Making Cations Main Group vs Transition Metals Electron Configurations Size Ionization Energy Making Anions Electron Configurations Size Electron Affinity Metallic Character Patterns in Chemical Reactivity 2 Ch08
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The size of Atoms The electron cloud of an atom defines it’s size. How do you measure the size of a cloud? The edges of a cloud are uncertain. We measure the distance between two adjacent atoms. Atomic size is measured by packing atoms close together, finding the distance between adjacent nuclei, and dividing that number by 2. Atoms can be packed densely by capturing them in solid form or capturing them in a another compound that is a solid. These atoms are not bonded, their electron orbitals don’t mix. We describe the atomic size we get from this process as the nonbonding atomic radius or van der Waals radius . For metals this involves analyzing metallic crystals (atoms held together with metallic bonds). For non-metals, we look at a large number of compounds that contain the element. We look at the average bond length between atoms. There is overlap between the electron orbitals. We describe the atomic radius found from covalently bonded compounds as the bonding atomic radius or covalent radius . Which atomic radius we use depends on the context. When we say atomic radius , we more often mean bonding atomic radius. We can determine the relative atomic radius of two elements by their position in the periodic table. 3
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Exploring Trends in Electronic Structure Atomic Radius Non-Bonding Radius vs Bonding Radius Trends Across Periodic Table Down Periodic Table Transition Metals Magnetism Ions Making Cations Main Group vs Transition Metals Electron Configurations Size Ionization Energy Making Anions Electron Configurations Size Electron Affinity Metallic Character Patterns in Chemical Reactivity 4 Ch08
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Relative Atomic Radius In general, as we move across the periodic table left to right the atomic radius decreases . Transition metals of the same period are roughly the same size. In general, as we move down the periodic table the atomic radius increases . 5
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Atomic Size Increases as we go Down Atomic Radius increases as we move down the periodic table because each period represents a new electron shell.
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