1. Periodicity: The arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group.

2. Atomic Radii- one-half the distance between the nuclei of identical atoms that are bonded together.

3. Trend: Increasing size

4. Atomic Radii- Why do atoms get smaller as you go from left to right across a period? periodic trends- atoms get smaller as you go from left to right because of an increasing positive charge of the nucleus more protons (+) = more pull on electrons (-) = smaller atom group trends- radii get larger down a group because of electrons occupying more energy levels and sublevels more electrons in more energy levels = bigger atom Why do atoms get larger as you go down a group?

5. Atomic Radius: Increasing size (more energy levels) Increasing size (Less protons to pull on electrons)

6. Which has the greater atomic radius, C or O?

7. Which has the greater atomic size, Li or K?

8. Ionization energy- the energy required to remove one electron from a neutral atom of an element

9. Trend:

10. Ionization Energy Why does it take more energy to remove an electron (ionize) as you go from left to right? periodic trends-energy increases across the period because of increasing nuclear charge (as you go left to right, the atomic number increases so the number of protons increases so the charge increases) (more protons = more pull on electrons = harder to remove) group trends-decrease down the group because electrons are farther away from nucleus. (electrons further from nucleus = less pull on electrons = easier to remove) Why does it take less energy to remove an electron (ionize) as you go down a group?

11. Ionization Energy: Increasing energy (Electrons closer to nucleus =harder to remove Increasing energy (More protons = harder to remove electrons)

12. Which has the higher ionization energy, Mg or P?

13. Which has the higher ionization energy, As or Sb?

14. Electronegativity Electronegativity: a measure of the ability of an atom in a chemical compound to attract electrons.(does not apply to noble gasses. They don’t form compounds) Which atom is more electronegative?

15. Trend:

16. Electronegativity Why do atoms attract electrons more as you go from left to right? periodic trends- increases across each period because of greater nuclear charge in the atom (does not apply to noble gasses) more protons = more pull on electrons group trends-decreases or stays the same down a group because electrons are further away from the nucleus. electrons further from nucleus = less pull on electrons Why do atoms attract electrons less as you go down a group?

17. Electronegativity: Increasing (Electrons closer to nucleus = morepull on electrons) Increasing (More protons = more pull on electrons)

18. Which has a higher electronegativity, C or O?

19. Which has the electronegativity, As or Sb?

20. Ionic Radii- A cation (a positive ion) formed when a neutral atom loses electrons An anion (a negative ion) is formed when an atom gains electrons

21. Ionic Radii Why do atoms get smaller when they lose electrons? trend- when a neutral atom becomes a cation (+) its radius decreases due to a lower number of electrons in the electron cloud Less electrons = smaller electron cloud = smaller atom Trend- when a neutral atom becomes an anion (-) its radius increases due to a higher number of electrons in the electron cloud. More electrons = larger electron cloud = larger atom Why do atoms get larger when they gain electrons?

24. Increasing: Ionization energy, Electronegativity, Increasing: Atomic radius (size) Label your periodic table:

25. Which atom is more electronegative? Mg or Sr

26. Which atom has a higher ionization energy? Pd or Cd

27. Which atom has a larger radius? P or Sb

28. Which atom has a larger radius? Ag or Ag 2+

29. Which atom is smaller in size? Ba or Cr

30. Which atom requires more energy to ionize? Sn or Ne