Shielding Effect

Kernel electrons block the attractive force of the nucleus from the valence electrons

+nucleus

Valence

Electrons--

- -

Electron

Shield“kernel”

electrons

http://www.bcpl.net/~kdrews/properties/properties.html#Atomic

ATOMIC RADIUS

Periodic Trends in Atomic Radii

LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 175

ELECTRONEGATIVITY—a measure of how strongly an atom’s nucleus pulls electron density toward itself when in a bond.

*assigned (Pauling scale)

*only useful in comparing two atoms (MEANS THAT ALL YOU CARE ABOUT IS THE DIFFERENCE!!!!)

Which has greater electronegativity in each compound?

IONIZATION ENERGY—a measure of how strongly an atom hold onto its electrons

*Ionization—removal of electrons1st: Atom A +I1 Ion A+ + free e-2nd: Ion A+ + I2 Ion A+2 + free e-

• It REQUIRES you to put in energy (excite the electron until it pops off)

• the more tightly an electron is held, the more energy is required