December 13

Thursday, December 13, 2012

Due Tomorrow: Periodicity Worksheet. The Alternate Universe Chemistry worksheet is not due until Monday. THE TEST HAS BEEN MOVED TO TUESDAY, 12/18.

Today in class, we spent the majority of the class going over the class notes. We learned about atomic radius, ionization energy, and a little bit of electronegativity.

     Atomic radius, simply put, is the radius, or size, of an atom. We learned that similarly to the Periodic Table of the Aliens, as you move up and down columns and left to right through the rows of the periodic table, the elements have similarities as well as one or two changing variables. For atomic radius, as you move left to right on the periodic table, the radius decreases. This is because as you move left to right, the elements have more protons, which bond with the electrons, drawing the atom tighter together, making the radius smaller. We also noticed the trend that, as you move down the families, the radii increases because there are more electrons as you move down, but not as many protons, which means that the size (radius) will increase. This trend is the opposite for both ionization energy and electronegativity.

     Ionization energy is the amount of energy required to remove one valance electron (an electron on the outer shell of the atom) from the atom. As I mentioned above, the trends of ionization energy are opposite to the trends of the atomic radius. As you move from left to right on a period, the energy needed to remove one electron increases. This is because as you move across the period, as mentioned above, the elements gain protons, drawing the atoms tighter together. Because the elements become more compact, the energy needed to pull one electron out increases. Similarly, as mentioned above, as you move down a family, the amount of electrons increase, but the amount of protons does not, so the atoms are less compact. This makes the amount of energy needed to pull out one electron less.

     The trends of electronegativity are exactly the same as ionization energy, for similar reasons. Electronegativity is the ability of an atom to attract electrons. As you move left to right across a period, the outer shell of atoms becomes more full. This means that as you move left to right, atoms need less and less electrons. The pull that they have to complete their electron shells becomes greater.

Go on Moodle if you need tonight's homework.

The next scribe will be.... Jack M.