Atomic Radii Ionic Radii Ionization Energies Electronegativity Periodic Trends Atomic Radii Ionic Radii Ionization Energies Electronegativity

Atomic Radius- used to estimate size of atom half the distance between two nuclei of identical atoms that are bonded together. Why?

Atomic Radii - Periodic Trends Notice atomic radii increase as we go down a group. Why? Notice they decrease as we go across a period from left to right even though we’re adding particles to the succeeding atoms. As we add more energy levels, size of atom increases As we move across period, atomic # increases, so electrons in s and p sublevels are pulled closer to the more highly charged + nucleus -> smaller radius

Ionic radius An ion is an atom or molecule that has gained or lost an electron. A cation is a positive ion How could an atom have a positive charge? A negative ion is called an anion. How could an atom have a negative charge? Atoms – lose electrons ,+ ions, smaller radius Atoms – gain electrons, -ions, larger radius Trend???

Ionization Energy energy required to remove an electron from an atom Can you predict which elements would require the least energy to remove an electron and which would require the most?

Ionization energy Period trend – increases as move across period, increased nuclear charge, higher +charge more strongly attracts electrons Group trend – decreases as move down a group; electrons in higher energy levels are farther from the nucleus making them easier to remove

Ionization Energy Factors affecting ionization energies include: Nuclear charge - The larger the nuclear charge the greater the ionization energy. Shielding effect - The greater the shielding effect, the less the ionization energy. Radius - The greater the distance between the nucleus and the outer electrons of an atom, the less the ionization energy.

Shielding effect Nuclear force absorbed By inner shell electrons e- e- Nucleus Outermost energy level with valence electron Inner (shielding) energy levels

Practice problems Pg. 165 #’s16-18

Electronegativity Electronegativity is the measure of an atom in a chemical compound to attract electrons. Increases as move up a group and across a period from left to right