Trends in the periodic table Ionization Energy Atomic

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

Background • 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 • 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

Atomic radius vs. atomic number

Answers 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

7. 11 p+ 12 n° 10 p+ 10 n° Na has 11 electrons Na+ has 10 electrons Ne has 10 electrons electron configuration of Na+ resembles Ne Alkali metals become like noble gases 8. 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

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. Li (enc = 1) ++ + Be (enc = 2) ++ + + B (enc = 3) +++ ++

10. Noble gases are ignored 11. 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 12. 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

Answers 2 a) – He, Ne, Ar (1), Noble gases (1) 2 b) – Li, Na, K (1), Alkali metals (1) 3 a) – Li, Na, K, Alkali metals (1) 3 b) – He, Ne, Ar, Noble gases (1) 4. As one increases, the other decreases (1) 5. Ionization energy increases (1) Atomic radius decreases (1) 6. Ionization energy decreases (1) Atomic radius increases (1) /11

7. 11 p+ 12 n° 10 p+ 10 n° Na has 11 electrons Na+ has 10 electrons Ne has 10 electrons Diagram of Na(1) & Na+(1), Na+ resembles Ne (1) Alkali metals become like noble gases (1) 8. Radius increases because shells are added (1) Increased radius will make it easier to lose an electron because of greater distance between positive and negative charges (1) /6

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

10. Noble gases are ignored (1) 11. Electron affinity is energy associated with an atom gaining an electron (1). It is highest in the top right (1) where atoms are smallest with the greatest number of protons 12. Electronegativity is a number that describes the relative ability of an atom (when bonded) to attract electrons (1). The trend is the same as affinity (1) for the same reason 9 – 10: /7 Total: /24 Note: graphs from day 1 were marked separately For more lessons, visit www. chalkbored. com