PERIODIC PROPERTIES
1. EFFECTIVE NUCLEAR CHARGE: The nuclear charge, Z, is the charge
of the nucleus. The effective nuclear charge, Zeff, is the amount of
positive charge on the nucleus perceived by an electron. Electrons
intervening between the nucleus and an outer electron are said to shield
or screen the outer electron from the nucleus so that the outer
electron does not experience the full nuclear charge.
EFFECTIVE NUCLEAR CHARGE= protons (nuclear charge) - Inner core
electron
FAMILY: As you go down in a family, the effective nuclear is more
difficult to talk about. It is better to talk about nuclear attraction of
the protons becoming weaker because the radius of the atom is getting
larger and the distance is greater thus the pull is weaker. The inner
core electrons are shielding the pull of the nucleus.
ROW: As you go from left to right in a row, the effective nuclear
charge, increases because the numbers of protons are increasing while
the inner core electrons are the same.
2. NUCLEAR ATTRACTION/CHARGE: pull of the electrons (Z)
FAMILY: Decreases as you go down a family because quantum levels are
added, the radius is increasing as well.
ROW: Increases as you go from left to right because the atoms are adding
on protons and the attraction becomes stronger.
3. IONIZATION ENERGY- the energy required to remove one electron
from a neutral atom of an element to make it an ion.
Ex: Li + energy → Li+
FAMILY: As you go down in a family the IE decreases because energy
levels are added on (radius increases) and the pull of the nucleus is weaker
thus allowing electrons to be taken of easier.
ROW: As you go from left to right in a row, IE increases because the
atomic radius decreases and the electrons feel a greater attraction to the
nucleus and thus making it more difficult to remove an electron.
EXCEPTIONS TO THIS TREND:
 An exception to this trend is when electrons are being removed from
different subshells. The electron removed from Be comes from the
2s orbital. The 2p orbital is slightly higher in energy than the 2s, so
the electron is easier to remove.
 2nd exception is Oxygen: The ionization energy for oxygen is lower
than expected. This due to the repulsions the paired electrons
experience in the filled orbital. The electron which is added is to
oxygen is a higher energy level due to repulsions it feels from the
other electron and therefore it is easier to remove.
4. ATOMIC RADIUS: the distance between the nuclei and the outermost
electrons in the valence shell.
FAMILY: As you go down in a family the radius increases because atoms are
increasing principal quantum levels thus making the atom larger.
ROW: As you go from left to right the radius of an atom decreases because
the inner core electrons remain the same but the nuclear charge increases
thus the electrons are being pulled more strongly and shrinking the atom.
5. IONIC RADIUS: the distance between the nuclei and the outermost
electrons of a cation/anion.
FAMILY: As you go from top to bottom the radius increases because ions
are increasing quantum levels thus making the ion larger.
ROW: Difficult to show trend. Cations are smaller than anions. The cation
formed when one or more electrons are lost has a smaller ionic radius
compared to the neutral atom. The loss of valence electrons yields a cation.
6. SHIELDING EFFECT: All electrons located between a given electron and
the nucleus screen, or shield, shield that electron from the full attractive
force of the nucleus.
FAMILY: As you go down in a family shielding increase because an atom is
adding on additional energy levels and thus adding more electrons.
ROW: As you go from left to right in a row, shielding effect stays the same
because the inner core electrons are the same for any given atom in that
row.
7. ELECTRONEGATIVITY: The measure of the ability of an atom in a
chemical compound to attract electrons. The EN is related to ionization
energy and electron affinity.
FAMILY: As you go down in a family electronegativity decreases because
the nuclear attraction decrease as electrons are added on in the quantum
levels
ROW: As you go from left to right electonegativity increases because
nuclear attraction, effective nuclear charge and ionization energy increase
thus increasing the ability of the atom to pull an electron.
8. ELECTRON AFFINITY:
is acquired by a neutral atom
energy change that occurs when an electron