Trends in the periodic table: Ionization Energy Atomic Radius Electron Affinity Electronegativity

Background 04/10/99 Electrons can jump between shells (Bohr’s model supported by line spectra) The electrons can be pushed so far that they escape the attraction of the nucleus Losing an electron is called ionization An ion is an atom that has either a net positive or net negative charge Q: what would the charge be on an atom that lost an electron? Gained two electrons? A: +1 (because your losing a -ve electron) A: -2 (because you gain 2 -ve electrons)

Ionization energy 04/10/99 Ionization energy is the energy required to remove one outer electron from an atom We will be examining the trends in ionization energy in groups and periods Handout Note: atomic radius is the distance from the nucleus to the outer electron shell Follow directions on sheet and answer questions (you can use textbook for help) Ignore H when looking at trends, look at many periods/groups when summarizing trends

Periodic table trends Answers

Ionization energy vs. atomic number 04/10/99

Atomic radius vs. atomic number 04/10/99

Answers 2 a) – He, Ne, Ar, Noble gases 2 b) – Li, Na, K, Alkali metals 04/10/99 2 a) – He, Ne, Ar, Noble gases 2 b) – Li, Na, K, Alkali metals 3 a) – Li, Na, K, Alkali metals 3 b) – He, Ne, Ar, Noble gases 4. As one increases, the other decreases 5. Ionization energy increases Atomic radius decreases 6. Ionization energy decreases Atomic radius increases

electron configuration of Na+ resembles Ne 04/10/99 7. 11p+ 12n° 11p+ 12n° 10p+ 10n° Na has 11 electrons Na+ has 10 electrons Ne has 10 electrons electron configuration of Na+ resembles Ne Alkali metals become like noble gases Radius increases because shells are added Increased radius will make it easier to lose an electron because of greater distance between positive and negative charges

Li (enc = 1) Be (enc = 2) B (enc = 3) + + + + + + + + + + + + 9. Proton # increases. More protons means greater attraction between nucleus and outer electron thus higher ionization energy. The greater attraction also means that outer electrons are brought closer to the nucleus, thus smaller atomic radius results. 04/10/99 Li (enc = 1) Be (enc = 2) B (enc = 3) + + + + + + + + + + + +

Noble gases are ignored Electron affinity is energy associated with an atom gaining an electron. It is highest in the top right where atoms are smallest with the greatest number of protons Electronegativity is a number that describes the relative ability of an atom (when bonded) to attract electrons. The trend is the same as affinity for the same reason 04/10/99