TRENDS IN THE PERIODIC TABLE

F. Schifano, Department of ScienceBayonne High SchoolBayonne, NJ

Key Skills

Navigate the periodic table

Consult the periodic table as a reference

Identify and use periodic trends

Atomic Radius

The “size” of the atom Measured as half the distance from

the nucleus of one atom to the nucleus of the next Border of the electron cloud is fuzzy Different atoms have different radii.

Atomic Radius Increases Down, Right

Anions

An atom can gain one or more electrons, forming a negatively charged anion.

Anions are larger than their neutral atoms.

Cations

Atoms can give up one or more electrons to form postively charged cations.

Cations are much smaller than their neutral atoms.

Ionic Radius

Cations (+) Anions (-)

Valence Runs the Show

What charge an atom will acquire when it becomes an ion is easily predicted using the atom’s valence.

Predicting Ionic Charge

Calculate Valence

Determine atom’s

simplest path to stability

Write newly formed ion

What ion is formed by each of the following?

Ba Ca Cl O Al

Which is larger?

Ba or Ba2+

Ca or Ca2+

Cl or Cl-

O or O2-

Al or Al3+

Ionization Energy— Breaking the “Binding Chain”

Ionization energy is the amount of energy in joules it takes to strip an electron off a neutral atom.

Electron Affinity– The “Joy” of Receiving a Gift Electron affinity is how much energy

in joules is released when an atom gains an electron. The number is given as a negative to

show that energy is released from the atom.

Both Ionization Properties Increase Up, Right

Both Ionization Properties Increase Up, Right Elements with low valence numbers

naturally lose electrons when they bond. Their electron affinities and ionization energies are both close to zero. They don’t fight losing electrons and

they don’t take much joy in gaining electrons.

Both Ionization Properties Increase Up, Right Elements with high valence numbers

naturally gain electrons when they bond. Their ionization energies are both far from zero. They viciously defend their electrons,

and celebrate mightily when they get more.

Properties of the Families