III. Periodic Trends (p. 140 - 154) Ch. 5 - The Periodic Table III. Periodic Trends (p. 140 - 154)

Periodic Law When elements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals.

Three rules apply to all periodic trends 1. Electrons are attracted to the protons in the nucleus 2. Electrons are repelled by other electrons in an atom 3. Completed shells are very stable

Atomic Radius Atomic Radius K Na Li Ar Ne

Atomic Radius Decreases to the RIGHT across a period Increases going down a group

Atomic Radius Why larger going down? Higher energy levels have larger orbitals Shielding - core e- block the attraction between the nucleus and the valence e- Why smaller to the right? Increased nuclear charge without additional shielding pulls e- in tighter

First Ionization Energy He Ne Ar Li Na K

First Ionization Energy Increases UP and to the RIGHT

Ionization Energy Why does it increase as we move right? As more protons are added to nucleus, the negatively charged e- are more strongly attracted which increases the energy required to remove them Why decrease down a group? Inner shells shield the outer valence electrons from the pulling power of the nucleus, making them easier to remove

Ionization Energy Successive Ionization Energies Large jump in I.E. occurs when a CORE e- is removed. Al 1st I.E. 577 kJ 2nd I.E. 1,815 kJ 3rd I.E. 2,740 kJ Core e- 4th I.E. 11,600 kJ

Electronegativity Moving across a period from left to right, electronegativity INCREASES. Moving down a group, electronegativity DECREASES.

Electron Affinity Electron Affinity – The energy change that occurs when an electron is acquired by a neutral atom. Most atoms release energy (negative values) If the electron causes the atom to have a more stable configuration then it releases a lot of energy.

Ionic Radii Cations – shrink because the nucleus is attracting fewer electrons Anions – expand because there is increased electron/electron repulsive forces Isoelectronic – Ions containing same # of electrons. Protons determine size

Melting/Boiling Point Highest in the middle of a period.

Examples Which atom has the larger radius? Be or Ba Ca or Br Ba Ca

Examples Which atom has the higher 1st I.E.? N or Bi Ba or Ne N Ne

Ch. 5 - The Periodic Table I. History (p. 123 - 127)

A. Mendeleev Dmitri Mendeleev (1869, Russian) Organized elements by increasing atomic mass. Elements with similar properties were grouped together.

A. Mendeleev Dmitri Mendeleev (1869, Russian) Predicted properties of undiscovered elements.

B. Moseley Henry Mosely (1913, British) Organized elements by increasing atomic number. Resolved discrepancies in Mendeleev’s arrangement.

Quick Review Who organized the elements according to atomic mass? Dimitri Mendeleev Correctly predicted properties of new unknown elements

What are Chemical Families? Elements with similar chemical properties Alkali Metals Alkaline Earth Metals Transition Metals Halogens Noble Gases

B. Chemical Reactivity Families Similar valence e- within a group result in similar chemical properties

B. Chemical Reactivity Alkali Metals Alkaline Earth Metals Transition Metals Halogens Noble Gases

Color Code the Following: -Group #’s +1 ions -Period #’s +2 ions -Lanthanides -1 ions -Actinides -Transition -Noble Gases Elements -Halogens

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