Periodicity

Friday, December 14, 2012

Due Monday: Alternate Universe Chemistry Worksheet and the Metal Reactivity Lab. The test is on Tuesday.

Today in class we learned everything there is to know about Periodicity. Mr. Lieberman showed us a couple of videos about how the Alkali Metals react with water. Then he showed us his own demonstration of how Aluminum and Magnesium react with air through a flame.  Aluminum had nearly no reaction and Magnesium had a vigorous reaction.  After this, we conducted our own lab to discover some periodic trends involving the reactivity of metals.

Reaction with Aluminum








Reaction with Magnesium

These were the results from my lab.  We tested reactivity of the metals: Calcium, Aluminum, and Magnesium with water and with Hydrochloric Acid.  We saw that Calcium was the most reactive in both cases.  We saw that Magnesium had a slight reaction with the two solutions.  We could not detect a reaction with the Aluminum in either of the solutions.  With this information, we could deduct certain information pertaining to periodic trends. We could clearly see that as you move across the periodic table, from left to right, reactivity decreases. (Magnesium more reactive than Aluminum.  We could also see that as you move down a column of the Periodic Table,  reactivity increases. (Calcium greater reaction than Magnesium)




Reactivity decreases for metals as you move across a row because it becomes harder for them them to lose electrons.  It increases as you move down a row because it becomes easier to lose an electron. We saw this in the videos we watched with the Alkali Metals. The reactions kept getting bigger and bigger all the way until Cesium's reaction with water made the bathtub explode.

The next scribe will be... JANE B

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.

Spectrum and quantum numbers

We started class by discussing about the electromagnetic spectrum. Mr. Lieberman then passed out these glasses to everyone in the room.

He told us to look at the lights in the room with the glasses on. You would see something similar to this.

These are called continues spectrum. The glasses makes the light bend into different colors. Then, he took out a tube filled with hydrogen gas. He put it in a machine that gives off energy. He then turn off all the lights, and this is what we see.

sorry its blurry!

Then, we put on our glasses, and this is what we see.

These are called line spectrum. Different frequency effects different wavelengths. Again, this happen because the glasses bends the light, making them break through its components.

We then go over the notes. We went over the Spectrum all the way to the quantum numbers. When there is energy, electrons jump up and then back down. When the electrons jump down, they release energy/light. We then went over quantum numbers. Here's a video explaining the quantum numbers.

Feel free to email Mr. Lieberman or go to the TLC if you still do not understand this.

HOMEWORK: Quantum Number worksheet and go on Moodle for a new schedule for this unit.


Next Scribe: Katie W.