Monday, February 13, 2017

Periodic Trends

It is all about the electrons! Always!

Electro- negativity is how badly atoms want electrons. The most electronegative atoms are Fluorine, Chlorine, and Oxygen. Everyone wants to be a Noble Gas... and halogens are the closest so they are the most electronegative.

Ionization energy is how difficult it is to remove electrons. It is difficult to remove electrons from atoms that are electronegative.

Atomic radius increases as you move down the periodic table because atoms have more mass, but actually decreases from left to right because atoms are holding on to their electrons tighter (because they are more electronegative).

Shielding has to do with how protons are blocked by the electron shells - the more shells there are, the more blocking there is. So something in period 5 (with 5 shells) has more shielding than an element in period 2 with two electron shells. Sheilding is constant across the periodic table because the number of shells is constant.

Compound Chemistry has an infographic on the Periodic Trends here

Friday, February 10, 2017

Electronic Configuration

Battleship, a classic game by Milton Bradley, is a game easily adaptable to learning electronic configuration.

Electronic Configuration is an intense mathematical calculation proposed by Schrodinger & Heisenberg as a way to predict where to find an electron around the nucleus in the electron cloud model. 

There are four main parts of the periodic table known as orbitals. The S block, P block, D and F orbitals. Within each block, you just count over how many spaces it is. There are seven energy levels that are loosely based on the period that an element is (the D & F blocks are exceptions to energy levels). The D block is dumb and that's why it starts with one number lower. Really they just have less energy and have the same amount of energy as the S and P block in the 3rd period. The F block are failures and that's why they are 2 lower... or they have a lot less energy.

So to identify Hydrogen you would say 1s2 because it is in the first period or first energy level, in the s block, and the first member of the first block. Carbon is a 2P2 because it is in the 2nd period, in the P block, and the 2nd one over in the P block.

Students learned the pattern of electronic configuration and how to use it. Basically its like giving directions to an element on the PT using set landmarks. It is a bit confusing, but once you get the pattern, its not too bad.

Students practiced a bit and then they played Battleship to practice some more. The Periodic Table became the game board and students hid their ships on it, then guessed hits using the electronic configuration of the atoms. I think they really got the hang of it because I did not field many questions at that point.

Thursday, February 9, 2017

Expanding your Horizons: Alkali Metals

This assignment, students will watch two videos about the reactions of Alkali Metals with water (HINT - They will explode!!!)

Video 1 - Alkali Metals in water, accurate!

Video 2 - Brainiac - Alkali Metals 

Tuesday, February 7, 2017

Dudes (Chemistry Scientists)

There are several "dudes," famous chemistry folks that students need to be familiar with. These dudes (Democritus, Dalton, JJ Thompson, Millikan, Rutherford, Bohr, Heisenberg, De Broglie, and Planck) all did experiments and came up with different and improved atom models. The current model is the elctron cloud or quantum mechanical model which was formulated by Heisenberg and De Broglie.

Heisenberg and De Broglie came up with the current electron cloud model, but we draw Bohr's planetary model the most often because it easier to count the electrons. There's a TedEd video about the progression - HERE.

Electrons are tricky because they move constantly and at high speeds. Heisenberg's Uncertainty Principle states that you cannot know both the speed and location of an electron - you can only know one - because measuring either one, changes the other. DeBroglie's wave theory helps explain why electrons sometimes act like particles and sometimes are compared to waves.

For more information about the evolution of the atomic model, check out this link. And here is a video!

Here are some Dude Quizlet Flashcards to help you out.

Monday, February 6, 2017

Atoms and the PT

Atoms, or elements, are the smallest unit of matter. They retain their identity in chemical reactions and are combined to form compounds and everything in the universe.

Atoms have some basic parts. Protons and Neutrons are found in the nucleus and make up the atomic mass. To find the number of neutrons, you subtract the atomic number (number of protons) from the atomic mass number (protons plus neutrons).

Electrons are so tiny that they do not influence the atomic mass. They are found orbiting the nucleus in shells or orbitals. Atoms are neutral so the number of protons equals the number of electrons.

How small is an atom? Watch this entertaining TedEd video!

Mendeleev designed the periodic table by looking at the properties of elements on cards and arranging them different ways until he got a system that worked. No one told him how to do it, he just did it until it worked. He even left spaces for elements that were discovered in his lifetime. (More info about Mendeleev) His periodic table was set up according to atomic mass number. The current table, altered slightly by Moseley, is organized by atomic number (number of protons). This is an AMAZING Video about Mendeleev and his PT!

Next we discussed regions of the periodic table, colored them, and labeled them. Periods are horizontal rows (periods go at the end of a sentence) and there are 7 periods. There are 18 groups or families (vertical columns) and a few of them have special names. This a pretty excellent diagram. This website gives a lot of helpful information.