2 Atomic RadiusAtomic radius = ½ the distance between the nuclei of diatomic moleculesX-ray diffraction = a way to estimate the distance between nuclei of atoms to determine their relative sizeDNA
3 Trends (general) Group – size increases as you move down Periodic – size decreases as you move left to right
4 Ionization EnergyThe energy required to remove an electron from a gaseous atomFirst ionization = removal of 1st outermost e-Second ionization = removal of outermost e- from 1+ ionAnd so on…This concept is used to predict ionic charges.
9 Summary Radii generally decrease across the periods Radii generally increase down the families Cations are smaller and anions are larger than neutral atoms of the elements from which they are formed Cations are generally smaller than anions Effective nuclear charge increases across each period
11 ElectronegativityElectronegativity is a measure of the tendency of an atom in a molecule or aggregate of atoms to attract electrons.Linus Pauling developed a scale of electronegativities so we use the Pauling as a unit
12 Summary: Electronegativity increases across the periods Electronegativity decreases down the familiesTrends are less regular for transition elements than for representative elementsMetals have low electronegativitiesFluorine and Oxygen are the two most electronegative elementsIonic bonds form between atoms of electronegativity difference of 1.7 or greater
14 Practice:How does the radius of an anion compare to the radius of a neutral atom for that element?Which element in each pair has a larger ionization energy: Na or K; Mg or P?For which of these properties does lithium have a larger value than potassium? 1st ionization energy, atomic radius, electronegativity, ionic radius?
15 Answers Anion is larger Na and P 1st ionization energy and electronegativityCheck out this site: