Periodic Trends: Atomic Radius PDF
Document Details
Uploaded by AdorablePraseodymium
2011
MsRazz ChemClass
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Summary
This PowerPoint presentation explains periodic trends in atomic radius. It details how atomic radius is measured and what factors influence it, including nuclear charge and shielding. The presentation also provides a visual aid using 'The Snowman' analogy to memorise the periodic trend.
Full Transcript
Day 2 - Notes Unit: Periodic Trends Trend for Atomic Radius (Size) Copyright © 2011 - MsRazz ChemClass After today, you will be able to… Explain how atomic...
Day 2 - Notes Unit: Periodic Trends Trend for Atomic Radius (Size) Copyright © 2011 - MsRazz ChemClass After today, you will be able to… Explain how atomic radius is found Explain the trend for atomic radius across periods and down groups Explain what shielding is, and describe the role it plays in atomic radius Copyright © 2011 - MsRazz ChemClass An atom does not have a fixed radius. The radius of an atom can only be found by measuring the distance between the nuclei of two touching atoms, and then halving that distance. Copyright © 2011 - MsRazz ChemClass Atomic Radius Atomic Radius: ½ of the distance between the nuclei of two like atoms Copyright © 2011 - MsRazz ChemClass The radius of an atom is dependent on: 1. Nuclear charge (magnitude of attraction from nucleus) 2. Distance between electrons and nucleus Copyright © 2011 - MsRazz ChemClass Period trend: (Across) atomic size decreases from left to right. These atoms have the same number of occupied energy levels, but a greater number of protons (increased nuclear charge). The energy levels are more attracted to the nucleus and are “pulled in.” Copyright © 2011 - MsRazz ChemClass Group trend: (Down) atomic size will increase as you move “ Wait! down a group Down a group, isn’t there an Moving down a group there increased nuclear is a greater number of occupied charge too?” energy levels (greater distance). Copyright © 2011 - MsRazz ChemClass Shielding Effect The inner electrons “shield” or block the attraction from the nucleus. While there is an increase in number of protons down a group (nuclear charge), this does not affect the magnitude of attraction from the nucleus due to this effect. Copyright © 2011 - MsRazz ChemClass Atomic Radii for Selected Atoms: Copyright © 2011 - MsRazz ChemClass Summary: Atomic Radius Increases Decreases Someone kicked down my snowman! Easy way to remember: THE SNOWMAN Copyright © 2011 - MsRazz ChemClass Then: Begin WS 2 (Homework) Copyright © 2011 - MsRazz ChemClass
