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 Size Within 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 Sizes cation positive ion atom LOSES electron(s) smaller than atoms from which they are made anion 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 Energy Within 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