Tuesday September 28, 2010.

Today Mr. Henderson started out the class by reviewing last nights scribe's blog. He went over all the plus points of it and went into further detail on how the blog reviewed what we did in class the previous day. He also talked about the 5 postulates. He then told us a little about what we were going to do today in class. Today in class our main goal was to learn about the atomic structure, atomic number, and the mass number.He then started to review page one in the packet. We went over most of it yesterday but we finished up today. We talked about how the Dalton theory of an atom was just a circle with the element name inside. There was no proposed structure to it. The JJ Thomson theory of an atom was that it looked like plum pudding. The Rutherford theory was that positive charges were concentrated in the nucleus which was in the center of the atom and then the electrons surrounded the empty space outside the nucleus. Bohr's theory of the atomic structure was that electrons are in orbit around the nucleus. Bohr's structure also only worked for hydrogen.The picture on the left shows these structures.

Before we continued our lesson on the atomic structure, Mr. H gave us a demonstration on how the cathode rays work. He gave us a little background information on who and how it started. In 1896 British physicist J.J Thomson showed the rays were composed of a previously unknown charged particle, which was later named the electron. The first picture shows the cathode ray empty. After putting some electricity conductivity you see a neon greenish light go through the tube. The second picture shows what happened when the electricity is conducted through the cathode tube and a magnet is put on top. The ray is reflexed to the top when the positive side of the magnet is put up. The third picture shows the same thing as in picture two just a variation. Picture number four is what the cathode ray looks like when the negative side of the magnet is put above it. Picture five is just what the cathode ray looks like when electricity is conducted through it.

1. 2. 3. 4. 5. 6.

After the completion of page one, and the demonstration, Mr.H gave us a little lesson on the atomic structure and there were notes on the board so we could follow along. The notes basically summarized everything that we needed to know to do page number two. The atomic number is the number

of protons plus the number of electrons. It is the identifying property of what the element is. The mass number is the number of protons plus the number neutrons. The mass number is on top and the atomic number is on the bottom as showed in the picture. On the other side of the atomic symbol there would be either a +, -, or no sign there. This determines the charge of the electron and the over all change. It also determines whether it is a positive, negative, or neutral charge. The symbol and the subscript go together. We then continued to talk about isotopes. Isotopes are different types of atoms of the same chemical element, each having a different number of neutrons. They also differ in mass but never in atomic number. The number of protons is the same because that is what characterizes a chemical element. We took the element carbon as an example. On the periodic table when you see the element carbon, you see its atomic symbol, the number of electrons its has, and you see a number at the bottom called the super script. The super script is the average of the mass number of the atomic element. For carbon on the periodic table it shows 12.01. This means that the most abundant isotope of carbon has a mass of 12.01. Mr. H then explained the different between an Ion and an Atom. An Ion is a charged particle while an atom is a neutral particle.

We then turned to page to and completed the chart. The chart helped practicing important skills such as knowing how to find the atomic number and the atomic mass and the number of protons and neutrons and the number of electrons of any given element. Here are the answers to the chart.

The last ten minutes of class we reviewed our unit one tests. Mr. H went over the frequently missed problems. He went into much detail on why these problems were wrong. Toward the end of class he passed out a sheet of paper called the "Mendeleev For a Day." There are 20 squares on this paper that you need to cut out for tomorrows class to play the game! Cant wait!