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Periodic Trends

Periodic Trends. Properties that Repeat. Periodic Trends . We will begin with an inquiry activity Using the table on the notes provided, use Table B.2 in the appendix section (pg. R47) to fill in the appropriate information. Make sure you include units where applicable. Mendeleev’s Table.

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Periodic Trends

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  1. Periodic Trends Properties that Repeat

  2. Periodic Trends • We will begin with an inquiry activity • Using the table on the notes provided, use Table B.2 in the appendix section (pg. R47) to fill in the appropriate information. • Make sure you include units where applicable.

  3. Mendeleev’s Table • Demitri Mendeleev, a Russian chemist, developed the first periodic table. • He arranged the elements known at the time in order of increasing atomic mass and also grouped them by similar properties.

  4. Follow this link to look carefully at Mendeleev’s first periodic table. • http://web.lemoyne.edu/~giunta/EA/MENDELEEVann.HTML The modern periodic table is based on increasing atomic numbers, which makes it slightly different than Mendeleev’s. Interestingly though, the elements still group by similar properties and elements were eventually discovered that filled in the “holes” of Mendeleev’s table and matched the properties that he predicted they would have.

  5. What does Periodic Mean? • Greek Roots PERI- meaning around HODOS- meaning paths In a periodic table, properties repeat from left to right What does PERIMETER mean? PERi - around METRON- to measure

  6. Major Divisions of Table • The major divisions of the periodic Table have different properties • Metals Nonmetals Metalloids Conduct heat Conduct electricity Have luster (shine) Ductile-make wires Malleable- make shapes Solids @ room temp. (except Hg) Poor conductor of heat Poor conductor of electricity Dull (don’t shine) Brittle- shatter when struck Most are gases@ room temp. Behave as a metal and nonmetal depending on conditions. Example: Silicon is a poor conductor but if you mix it with a small amount of Boron is a good conductor of electricity.

  7. Atomic Size (atomic radii) • Atoms don’t have sharply defined boundaries so we estimate their size by looking at the units or molecules they form when joined together. • When two identical atoms join to form a molecule, the distance between their nuclei can be used to estimate the size of each atom.

  8. The atomic radius is ½ the distance between the two nuclei. (note: ½ the distance is like measuring the radius of a circle).

  9. Ions- Refresher • Remember, metals tend to give away electrons (to be stable like the noble gases) and form positive ions • Na- 1s2 2s2 2p6 3s1 – gives away the 3s1 electron and now has this configuration, 1s2 2s2 2p6 • Na ion has 11 protons and 10 electrons and is Na+ (Remember Neon’s configuration is 1s2 2s2 2p6 )

  10. Nonmetals tend to accept electrons (to be stable like the noble gases) and form negative ions. • Fluorine – 1s2 2s2 2p5 will accept an electron and have a configuration of 1s2 2s2 2p6 (like Neon) The Fluorine ion now has 9 protons and 10 electrons and is negatively charged: F 1-

  11. Ionization Energy • Ionization energy is the energy required to remove an electron from an atom. • (Think about which type of atoms try to gain electrons and which try to lose electrons. Which of these types would require more energy to take one of their electrons? The ones trying already to get rid of them or the ones trying to get more electrons?)

  12. The FIRST ionization energy (which we will be working with) is the energy required to remove the FIRST electron from an atom. • The SECOND ionization energy is the energy required to pry off an electron from a 1+ ion (the result is a 2+ ion) • The THIRD ionization energy is the energy required to pry yet another electron from a 2+ ion (the result is a 3+ ion).

  13. QUESTIONS (for you toanswer) • 1- Which type of element do you think would have the highest ionization energy, Metals or nonmetals? EXPLAIN

  14. Ionic Size or Ionic Radii (radii of ions) • During chemical reactions between metals and nonmetals; metal atoms tend to lose electrons to nonmetals that gain those electrons. • The transfer of electrons between them predicts the size of ions they form.

  15. Ionic Radii cont. • Cations (positive ions) are smaller than the atoms that form them. Question: Why do you think this is true?

  16. Ionic Radii cont. • Anions (negative ions) are larger than the atom that forms them. Question: Why do you think this is true?

  17. Electronegativity • Electronegativity is the ability of an atom or element to attract electrons WHEN the atom is in a compound? In this picture the electron cloud is larger around the Fluorine atom (nonmetals try to get electrons) so the fluorine even though it is sharing electrons with hydrogen, attracts the electrons from both atoms more strongly than hydrogen does.

  18. The table below shows the electronegativity values for elements.

  19. QUESTIONS: 1- Write the electronegativity value for H; and for F. Which one is higher? Which atom is more likely to attract electrons when in a compound? 2- Why aren’t there any electronegativity values assigned for the noble gases?

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