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 –

** 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.

-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.