UNITS:- nanometres 11+ 17+
Effective Nuclear Charge (Zeff or ENC) describes the idea that core electrons of an atom can shield the attraction that valence electrons have toward the positively charged nucleus. In a way, the inner core electrons shield or reduce the attraction between the nucleus and the outermost electrons. We can think of the ENC as the attraction felt by the valence electrons to the nucleus. A higher Zeff value means that the nucleus has greater pull for valence electrons.
Across a period Zeff INCREASES. This results in smaller Atomic Radii Down a group Zeff DECREASES. This results in larger Atomic Radii
IONIC RADII- The radius of the ion - If positively charged ( cations) the radius decreases while if the charge is negatively ( anion) the radius increases (relative to the atom). - See your Bohr Diagram Note to witness the magic When substances have the same number of electrons (isoelectronic), the radius will depend upon which has the largest number of protons. E.g. Predict which of the following substances has the largest radius: P 3 , S 2 , Cl 1 , Ar, K + , Ca 2+ .
1st IONIZATION ENERGY Definition The energy required to remove ONE electron from the valence shell of an atom X (g) X + (g) + e - Make sure you write in the (g) Make sure you write in the (g)
FIRST IONIZATION ENERGY