SG Chemistry 2A Week 7 Blog

To start this week off with a fun activity, Dr. Finnan did two demonstrations for us. For the first demonstration, as shown on the left, he took a copper sheet and used a burner on it. It was very interesting to observe as the copper turned black where it was being heated. He then turned it around and heated the other side, and everyone was fascinated as the color turned back to the state before it was burned. This, as he explained, was due the electrons jumping from the heat and the charge of copper. The next demonstration was a magnesium and oxygen reaction. As shown in the picture, the substance burned very brightly and was fascinating to watch. These activities moved us into our next unit of naming compounds, and the difference between ionic and molecular compounds.

This was a very useful unit for me in which I learned a lot, and made things a lot easier when explaining so that I didn't have to say awkward letters instead of the correct names of the compounds. To begin the unit we worked on a POGIL called naming ionic compounds. With this worksheet we worked together in table groups and discovered that ions have charges: either positive, cation, or negative, anion. We weren't sure what causes these charges or why some ions can have two different charges. I concluded it must be because of the number of electrons, but I am still unsure about why the electrons give off that specific charge for different elements.

At first, naming ionic compounds was confusing for me. I didn't know how to specify how many of each ion goes into the compound in its name. But then I learned that in naming these type of compounds, you don't have to specify how many ions there are because the charges always have to cancel out and then therefore the ratio may be inferred by the name. But what about ions the don't have a constant charge? I found myself asking. It wasn't until later in the week that we learned we specify the charge with Roman numerals ( i.e if we were using the single charge of copper, after writing copper we would write (I) in order to represent this). Then the second ion’s ending is either replaced with ‘ide’, if it is a binary compound, but if the second ion is polyatomic, then we use the name already given for it.

Because I struggled a lot naming ionic compounds, when we moved on to naming molecular compounds it came much more naturally to me. One thing I found surprising about the big difference between molecular and ionic compounds, is that always in the name of a molecular compound, the number of ions in each element is always specified. We specify this with prefixes such as mono, meaning one, di, meaning two, and tri meaning 3 and so on. Because I had worked with these prefixes in other classes, I was very familiar with them and they came very naturally to me when using them.

The biggest thing that I struggled with this unit was distinguishing between an ionic compound and a molecular compound. It wasn't until the weekend before the test that I realized that ionic compounds always contain metals that form one ion, and molecular compounds only contain non-metals. After I realized this things got a lot clearer and I did much better on the test. Although we haven't gotten into it that much, I'm still curious to know why some ions don't have charges that cancel, and ultimately what even causes an ion to have a charge.