# 06.13.2019: One Chapter of Science – The Periodic Table, Atomic Structure, and Compounds

Today’s soundtrack is Wovenhand: Wovenhand, a gothic country rock album that reminds me somewhat of a darker take on Eddie Vedder’s “Into the Wild” soundtrack, with deeply spiritual lyrics. Wovenhand is an album best experienced while walking on a forest path in the early morning.

This morning, I’m reading the seventh chapter of Everything You Need to Ace Science in One Big Fat Notebook, “Periodic Table, Atomic Structure, and Compounds.”

As we learned last time, all matter is made of atoms. What form (solid, liquid, vapour) the matter takes depends on how quickly or slowly the particles (protons, electrons, and neutrons) are moving around. But different kinds of matter react differently to various external forces. What determines the makeup of a given kind of matter? The makeup of the atoms! Each atom is made up of certain number of protons and electrons. The number of each determines what element the atom will make. Scientists have listed the 118 known elements in the periodic table, a bunch of boxes made up of big letters and little numbers. Inside of each box is an element’s chemical symbol. A chemical symbol represents an element.

A more descriptive form of the periodic table’s elements include, from top to bottom, the atomic number, chemical symbol, element name, and average atomic mass.

The atomic number tells us how many protons are in an atom. Every atom will have the same number of electrons and protons.

The atomic mass tells us how much mass a single atom of an element will have.

The periodic table, being a table, is made up of rows and columns. The rows are called periods, and the columns are called families. The elements are arranged from left to right by lowest to highest number of protons, and are often colour-coded to show the different families, which “share similar chemical and physical properties” (p. 74).

We know that the electrons orbit the cluster of neutrons and protons that reside at the centre of every atom. But is there a method to their orbits? Yes! The elctrons orbit at varying discrete distances from the nucleus, and only a certain number of electrons can orbit at each distance. Those closest to the nucleus are the most attracted to the nucleus; there can be a maximum of two electrons at this orbit level (which is called an energy level). All the other energy levels that are further out from the nucleus can each have a maximum of eight electrons.

So we now know that every element has the same number of electrons as it has protons…but what of the protons? The number of neutrons in an atom does not coincide with the number of protons or electrons. So if we put two atoms beside each other, both containing the same number of protons and electrons, but each with a different number of neutrons, we would have two isotopes, which are “[a]toms of the same element that have a different number of neutrons” (p. 76). The atom with more neutrons would be heavier; its atomic mass would be greater. We can determine the number of neutrons in any element by subtracting its atomic number from its average atomic mass (rounded to the nearest whole number).

Atoms can be charged either positively or negatively. Doing so converts some of their electrons into protons or vice versa. Atoms can also be combined with other atoms to form molecules, and molecules can be combined with each other to make molecular compounds. A common example of this idea is the diatomic (two-atom) molecule O₂.

Remember the energy levels that we talked about earlier? They’re the different distances that electrons orbit the nucleus of an atom at. The furthest energy level from the nucleus is called the valence shell, and only the electrons in this shell, called valence electrons, will combine with the electrons of another atom.

So how do we put this all together? Where does the chemical formula H₂O come from? Well, each chemical formula is simply made up of the chemical symbol and the number of atoms found in the compound. So one molecule of water is made of two atoms of hydrogen and one atom of oxygen.

Summary:

1. There are approximately 118 known elements
2. Elements are differentiated by their atomic numbers
3. The name of a column of elements in the periodic table is a group or family; these have similar physical and chemical properties
4. Two or more atoms combine to form a molecular compound molecule
5. The atomic mass of an atom is the typical mass of an element’s atom
6. If the atomic number of an element is 6 and the atomic mass is 15, there are nine neutrons present
7. An isotope is an element that has a different number of neutrons from another element that it has the same number of protons and electrons as.
8. A chemical bond is a joining of two atoms into a molecule a sharing of electrons between atoms
9. Atoms bond for increased stability

That’s it for today! Next time, we’ll be reading the eighth chapter.