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Relative Size

Relative Size. Ionization Energy. Electron Affinity. Electronegativity. General Rule - Relative Size. When looking at the periodic table, atoms get bigger: Top to bottom Right to left. http://www.lung-cancer-report.com/berylliosis-beryllium/picture-of-beryllium-atom.html.

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Relative Size

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  1. Relative Size Ionization Energy Electron Affinity Electronegativity

  2. General Rule - Relative Size • When looking at the periodic table, atoms get bigger: • Top to bottom • Right to left http://www.lung-cancer-report.com/berylliosis-beryllium/picture-of-beryllium-atom.html

  3. Top to Bottom Down a Column The atoms get bigger because the electrons are in a higher energy level.

  4. Left to Right Across a Row The atoms get smaller because the positive charge in the middle of the atom is more concentrated so it’s sucking the electrons in closer.

  5. Relative Size Chart http://www.iun.edu/~cpanhd/C101webnotes/modern-atomic-theory/atomic-radii.html

  6. *Positive Ions and Negative Ions* • Positive Ions: If an atom loses all of its valence (outermost) electrons, it’s going down to the next energy level so it’s getting smaller. • Losing electrons = positive charge • More protons than electrons = + charge

  7. *Positive Ions and Negative Ions* • Negative Ions: If an atom gains electrons it has a negative charge. The nucleus stays the same but the radius gets bigger because there are more electrons. • Gaining electrons = negative charge • More electrons than protons = - charge

  8. Sample Problems - Part 1 Which one has a larger radius? (a) Ti or Ni (b) F or F-1 (c) Ba or Hf (d) Ca or Ca+2

  9. Sample Problems - Part 2 Which one has a smaller radius? (a) K or Cs (b) Cs or Os (c) O or O-2 (d) Na or Na+1

  10. Challenge Excluding the Noble Gases because they’re special: What is the smallest atom? ____________________ What is the largest atom? ____________________

  11. IonizationEnergy Definition: The energy required to remove an electron from an atom. First Ionization Energy • The energy needed to remove the most loosely held electron from an atom. • Measured in kilojoules per mole (kj/mol).

  12. General Rule - Ionization Energy • Ionization Energy increases going across periods (rows) - increases as atomic number increases. • Ionization Energy decreases going down groups (columns).

  13. Classifying Elements based on Ionization Energy • Metals • Tend to lose electrons to become more stable • Low ionization energy • Nonmetals • Tend to gain electrons to become more stable • High ionization energy • Noble Gases • Have an octet so they’re already stable • Very high ionization energy

  14. Electron Affinity Definition: the attraction of an atom for an additional electron • Metals tend to have low electron affinities. • Nonmetals tend to have high electron affinities.

  15. Sample Problems - Part 3 • Which one has a lower ionization energy? (a) Cl or Kr (b) Iron or Iodine • Which one has a higher electron affinity? (a) Oxygen or Barium (b) Na or Cl

  16. Electronegativity Definition: the relative attraction of an atom for a shared pair of electrons. • The difference in electronegativities increases as the bond strength between two atoms increases. • Metals tend to have low electronegativities. • Nonmetals tend to have high electronegativities.

  17. Electronegativity Chart www.monroecc.edu/wusers/flanzafame/PerElNegativity.pdf

  18. Sample Problems - Part 4 • Which atom has a higher electronegativity? (a) Ca or C (b) Titanium or Tellurium • Which atom has a lower electronegativity? (a) Br or Be (b) Strontium or Selenium

  19. Factors that affect Ionization Energy, Electron Affinity, and Electronegativity • Distance from nucleus • Stability

  20. Connections between Ionization Energy,Electron Affinity, andElectronegativity • In general, as Electron Affinity increases, Ionization Energy increases. • Electron Affinity and Electronegativity increase going across a period (left to right). • Ionization Energy and Electronegativity increase going up a column (bottom to top).

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