MP 3 Quiz: Factors that Affect Periodic Trends
Students should know:
1. The five periodic trends we will study in detail: atomic radius; ionic radius; metallic character;
electronegativity and ionization energy.
2. Metallic character – how loosely an atom holds its electrons
3. Electronegativity – the ability of an atom to attract electrons to itself
4. Ionization energy – the amount of energy necessary to remove an electron from an atom in the
gaseous state
5. The three factors that affect periodic trends:
(1) Effective Nuclear Charge – the ability of the nucleus to hold onto its electrons can be
calculated based on the following formula: Zeff = Z – S; where  Zeff is the Effective Nuclear Charge
 Z = number of protons
 S = the shielding constant – see below
(2) Shielding – the electrons that block or shield the valence electrons from feeling the full force
of the nucleus – can be calculated using the following formula:
S = total # of electrons – valence electrons
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(3) Coulomb’s Law – a physics law that relates the product of the charges (positive nucleus and
negative electrons) and the distance of the electrons from the nucleus – as the size of the
atom increases – the radius of the atom increases and the distance between the valence
electrons and the nucleus increases and the force of attraction between the nucleus and the
valence electrons decreases.
Be able to calculate Zeff, and S.
Be able to explain what happens to the effective nuclear charge as you go from left to right
across the periodic table
Be able to explain what happens the effective nuclear charge as you go down a group in the
periodic table
Be able to explain what happens to the shielding as you go from left to right across the periodic
table
Be able to explain what happens to the shielding as you go down a group in the periodic table