2E

Peridoic Table - Chem - Quarter 3 

7.1: Development of the Periodic Table

Mendeleev and Meyer recognized predictable patterns in elements as atomic weight increased

Moseley developed atomic numbers

7.2: Effective Nuclear Charge

Properties of the atom depend on electron configuration and how the attraction between electrons and the nucleus

Electron- electron repulsion-- same charge

  • Cancel some of the electron nucleus attraction
  • More electrons= more repulsion= less attraction between nucleus and electron
  • Effective nuclear charge- net attraction
    • Less than the actual nuclear charge
    • increases right to left across a periodic table
    • Number of core electrons stays the same; the number of protons increases
    • increases slightly as we go down a column

7.3: Sizes of Atoms and Ions

bonding atomic radius: shortest distance between the two nuclei during an atomic collision divided by 2

bonding radius< non bonding radius

Atomic radius increases as you go down a column

  • Increasing n (energy levels) therefore greater probability of electrons being farther from the nucleus

Atomic radius decreases left to right

  • Effective nuclear charge decreases (less shielding ) and therefore increasing atomic radius

Cations are smaller than parent atoms

  • electron - electron repulsion is reduced

Anions are greater than parent atoms

  • electrons are added therefore electron- electron repulsion is increased, increasing radius

Isoelectronic series have the same number of electrons

  • When listed in increasing atomic number, nuclear charge increases ; electron number stays the same, but protons increase; stronger attraction of electrons to the nucleus; ionic radius decreases.

7.4: Ionization Energy

Ionization energy is the minimum energy needed to remove an electron from the ground state of an atom

  • Greater ionization energy = more difficulty removing electrons
  • first ionization energy is the smallest and increases with each successive ionization
  • Sharp increase in the ionization energy occurs when inner shell is removed
  • Always positive- energy must be absorbed to remove electrons

%%Ionization energy increases as we move across a period%%

  • Increase in effective nuclear charge and decrease in atomic radius

%%Ionization energy decreases are we move down a period%%

  • atomic radius increases

7.5: Electron Affinity

Electron affinity is the energy change that occurs when an electron is added to a gaseous atom

  • Energy is released--- answer is in negatives
    • Greater attraction between atom and added electron the more negative the answer
  • Energy change when atom gains and electron

7.6: Metals, Non-metals and Metalloids

Metals:

  • Low ionization energy
  • Loose electrons

Non Metals:

  • Gain electrons

Metalloids: in between the two

7.7: Trends for Group 1A and Group 2A Metal

Group 1A-- alkali metals

  • Low densities and melting points
  • Increasing atomic radius, decreasing ionization energy
  • Very reactive

Group 2A -- alkaline earth metals

  • Denser, higher melting points
  • Less reactive

7.8: Trends for Selected Nonmetals

Hydrogen is the most reactive

Oxygen is polar

7A is halogens

8A is noble gases-- not reactive

  • High first ioniization energy