 Without looking at your reference tables, write the names of these elements:  C, Ca, Co, Cr, Cu  In table S look up the atomic radius for each of these elements.

Properties that repeat in intervals Observable trends in the table

 Decreases going from left  right across a period.  Decreases going up from bottom to top in a group.  Practice: which is more metallic, Li or B?  Answer Li  Which is more metallic, Mg or Ba?  Answer Ba  Most metallic element is  Fr. Lease metallic element is:  He.

 Atomic radius is the size of an atom.  Measure the distance between nuclei of two touching atoms and taking half the distance

 Atomic radius of lithium =  Atomic radius of sodium is =  Atomic radius of potassium =  Trend is to increase as you go down a group  Because each period adds a new principal energy level (PEL)

 Atomic radius of lithium =  Atomic radius of beryllium is =  Atomic radius of boron =  Trend is to decrease as you go left  right across a period,  Because of increasing nuclear charge.  There are more protons to pull the electron cloud in closer.

 Biggest atom:  Francium  Smallest atom:  Helium

 The energy required to remove one valence electron from an atom in the gas phase.  Conversely (in other words): the energy an element possesses to hold on to its valence electrons.  Joules are a measure of energy. How many joules in a kJ?  I.E. of sodium:  I.E. of magnesium:

 I.E. of sodium: 496 kJ/mole  I.E. of magnesium: 738 kJ/mol  I.E. increases going from left  right across a period,  because of increasing nuclear charge.  More protons hold onto the electrons so it is harder to remove one.

 Practice (not in your packet but do it anyway):  What is the electron configuration of  Mg?  Sr?  What is the difference?  I.E. decreases going from top to bottom down a group,  because each period adds a PEL, and  therefore (-) outermost electrons are further from the (+) nucleus.

 The relative attraction for an electron from another atom in a bond.  An atom's "pull" (or envy) of an electron of another atom.  A covalent bond is a pair of shared electrons, but what if the sharing is not equal?

 How is it measured?  Arbitrary scale relative to Fluorine, which has electronegativity of 4.0  Eneg increases going from left  right (except noble gases),  because metals lose electrons easily.  Metals don't hold onto their electrons tightly.

 Decreases going from top to bottom,  because each period has another shell.  Electronegativity follows a similar pattern/trend as ionization energy except for the noble gases (group 18).  Noble gases have highest I.E., because they are stable and do not want to ionize.  Noble gases have no electronegativity because they have a full octet.

 Highest Eneg: F  Lowest Eneg: Fr

M = Metallic Character E = Electronegativity R = Atomic Radii I = Ionization Energy