Periodic Trends

Chemical Periodicity

Atoms participate in chemical reactions in order to fill their outermost s and p sublevels.

Some definitions… ionization energy – energy required to

remove an electron from an atom

electron affinity – energy required to add an electron to an atom

electronegativity – tendency of atoms to attract e- when they are bonded to another atom

Four Classes of Elements

Noble Gases outermost s, p filled do not react

Representative Elements outermost s or p only partially filled

Transition Metals outermost s filled adding e- to d sublevel

 

Inner Transition Metals outermost s sublevel is filled adding e- to f sublevel

Trends in Atomic SizeWithin Groups: size increases as you move down e- are being added to additional energy

levels

Within Periods: size decreases left to right because of

increase in effective nuclear charge larger # of p+ causes atom to “shrink” inner e- shield nucleus

Effective Nuclear Charge

Trends in Atomic Size

Trends in Ion Sizescation positive ion atom LOSES electron(s) smaller than atoms from which they are

madeanion negative ion atom GAINS electron(s) larger than atoms from which they are

made

Relative Sizes of Cations

Relative Sizes of Anions

Trends in Ionization EnergyWithin Groups: IE decreases as you move down

• e- are farther from nucleus• e- not held as tightly in larger atoms

Within Periods: IE increases from left to right nucleus has greater attraction for e- in

smaller atoms

Ionization Energy

Trends in Ionization Energy

Trends in Electronegativity

Within Groups: decreases as you move down atoms too large for nucleus to attract e-

Within Periods: increases left to right atoms get smaller, easier to attract e-

Trends in Electronegativity