Periodic Trends

1. Periodic Trends

2. Chemical Periodicity • Atoms participate in chemical reactions in order to fill their outermost s and p sublevels.

3. 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

4. Four Classes of Elements Noble Gases • outermost s, p filled • do not react Representative Elements • outermost s or p only partially filled

5. Transition Metals • outermost s filled • adding e- to d sublevel Inner Transition Metals • outermost s sublevel is filled • adding e- to f sublevel

6. 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

7. Effective Nuclear Charge

8. Trends in Atomic Size

10. 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

11. Relative Sizes of Cations

13. Relative Sizes of Anions

14. 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

15. Ionization Energy

16. Trends in Ionization Energy

17. 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-

18. Trends in Electronegativity