Agenda Block 4 Attendance Make Groups for element assignment What did we learn last class? What’s a trend? Get into your groups Discover a trend Preform your trend Homework-Part C and Part D

Periodic Table Trends WooT Get Excited!!!

PERIODIC TRENDS: Periodic trend -  

Atomic and Ionic Radii: Atomic size is usually described by the radius of an atom. Atomic radii - atomic radius usually determined by the distance between the nuclei of metal atoms in a crystal. (X-ray diffraction) Trend-

Ionic radii Def’n- is a measure of the size of the electron probability volume for an ion. i.e. Charged molecules will vary in size as electrons are received or lost. Atoms get going down a group. Atoms get moving from left to right across each period.

Why does radius get smaller as # of electrons increases as you move across a period? -higher atomic number - -more protons - -increased force of attraction causes to move closer to the nucleus. Why does radius get larger as you go down a group? -number of electrons -orbitals further and further from the nucleus -repulsive forces from inner electrons shields outer electrons from attractive forces of the nucleus. ( )

Shielding Effect  Decrease in attraction between an   in any atom with more than one electron shell.

Ionization Energy: Def’n- the minimum amount of energy needed to remove the most loosely bound electron from a gaseous atom to form an . element(g) + ionization energy --> Ionization energies enable scientists to predict which elements may form the positive ions in ionic substances. most likely to be positive ion. Atoms with ionization energies hold onto their electrons very tightly.

ex Noble gases - Alkali metals – ex Noble gases - Alkali metals – ** ionization energies decrease as you move down a group. Ionization energies increase as you move from left to right across a period. **

The difference between 1st, 2nd, and 3rd ionization energies is the increase in energy for every electron . (1st 2nd and 3rd) ex Magnesium 3rd IE is considerably higher because the first 2 are valence electrons.

Ionization energies: -decrease as you move down a group Ionization energies: -decrease as you move down a group. -increase as you move from left to right across a period.

Electron Affinity: Def’n- when an electron is added to an atom to form an ion with a 1- charge. Elements with electron affinities gain electrons easily to form negative ions (anions)

In general, non-metals have more negative electron affinities than the metals do. Non-metals release energy when they gain electrons. Metals have to gain energy before they gain an electron. ** electron affinity is more as you move up a group. EA is more as you move from left to right across a period**

Electronegativity:  Def’n- An atom’s ability to attract electrons in a chemical bond. Fluorine is the most electronegative element (4.0). Cesium and Francium have the least electronegativities (0.7). Electronegativity is used to . Large differences in EN react to form ionic compounds Small difference in EN usually form covalent compounds. (sharing of electrons)

** electronegativities usually from left to right across periods and from bottom to top within groups.** 

Metallic Properties: General properties of metals from right to left across periods and from top to bottom within groups.