I am trying to complete one of those charts, where you find an element, its proton number, its electron number, it's charge, and whether it's an ion or an atom, based on looking at the Periodic Table. I get how it works, sort of, like for Lithium, you look at the number at the top (3), the horizontal number (2), and subtract three from two. But when I tried this same method with other elements, like Chlorine, it didn't work. For example, chlorine was number 17, in column seventeen, but my teacher says the number of electrons should be 18. Why is this? Thank you!

I am trying to complete one of those charts, where you find an element, its proton number, its electron number, it's charge, and whether it's an ion or an atom, based on looking at the Periodic Table. I get how it works, sort of, like for Lithium, you look at the number at the top (3), the horizontal number (2), and subtract three from two. But when I tried this same method with other elements, like Chlorine, it didn't work. For example, chlorine was number 17, in column seventeen, but my teacher says the number of electrons should be 18. Why is this? Thank you!

In order to understand how to fill out the chart correctly, let's take a closer look at the concept of atomic number and electron configuration.

The atomic number represents the number of protons in an atom. It is also equal to the number of electrons in a neutral atom. For example, since Lithium has an atomic number of 3, it means it has 3 protons and 3 electrons.

The Periodic Table is organized in such a way that elements are arranged in order of increasing atomic number. As you move across a period (horizontal row), both the atomic number and the number of electrons increase by one for each subsequent element.

Now, let's consider Chlorine as an example. Chlorine has an atomic number of 17, which means it has 17 protons. However, your teacher correctly mentioned that the number of electrons for Chlorine should be 18. This is because chlorine belongs to Group 17 (or column 17) of the Periodic Table, which is known as the halogens. Halogens have seven valence electrons, which are the electrons in the outermost energy level. Since chlorine is in Group 17, it already has 7 valence electrons. Therefore, if we add the 7 valence electrons plus the 10 inner electrons, we get a total of 17 electrons in the atom.

It's important to note that when an atom gains or loses electrons, it becomes an ion. If an atom gains electrons, it becomes negatively charged and is called an anion. Conversely, if an atom loses electrons, it becomes positively charged and is called a cation. For the chart you are working on, make sure to indicate the charge of the ion or indicate "0" if it's an atom (neutral).

To summarize, when working with the chart:

1. Locate the element on the Periodic Table.
2. Identify its atomic number, which corresponds to the number of protons and electrons.
3. Consider the group (column) of the element to determine the number of valence electrons.
4. Add the number of valence electrons to the number of inner electrons to find the total number of electrons.
5. Determine if the element is an atom (neutral) or an ion by considering the charge. An atom will have a charge of zero, and an ion will have a positive or negative charge.

By following these steps and understanding the concept of valence electrons, you should be able to fill out the chart accurately for various elements.