As a homeschooling mom, I think hands on activities make learning science so much more interesting and fun. I also think they help children to understand science in a more concrete way. Things like atoms and molecules are pretty hard for a young child to comprehend without something tangible to relate to. In this post, and in a series of posts that will follow, I want to share with you some ideas for teaching elementary and middle school aged children about chemistry.
Let’s start with atoms and molecules.
What is an atom?
Atoms are tiny tiny particles that make up all matter. You can’t see them - in fact, they are so tiny that millions and millions of them can fit in the point of the very sharpest pencil. But eveything around us is made of millions and millions of atoms - our bodies, our homes, our pets, the trees, even the air we breathe! To help make this concept more concrete, take a look through a magnifying glass at an image in a book or a picture printed from your computer. This will work best with a magnifying glass that magnifies at 4X or higher.
What do you see? Can you see that the picture is made from many many tiny dots? When you look at the picture with just your eyes, you don’t see the dots, but the picture is really just a whole lot of tiny dots of color put together. Atoms are like this - only even smaller!
The Human Atom
This is a fun activity for a group of children. You build a model of an atom using people as the subatomic particles. You need one notecard for each child in the group. Divide the notecards into three equal groups (roughly) and write a minus sign on the notecards in one group, a plus sign on the second group of notecards, and a zero on the third group of notecards.
Give one notecard to each child in the group and explain that the protons are positive and they are found in the center of the atom, which is called the nucleus. The neutrons are neutral and also found in the nucleus. Protons and neutrons are roughly the same size and they are the largest of the three main subatomic particles. Have all the children with + or 0 cards form a group in the center of the room. If you are working with a multi-age group, give the smallest of the children the - cards and explain that electrons are negatively charged and they are the smallest of these three subatomic particles. Then have the “electrons” run around the nucleus, explaining how the electrons move around the nucleus in orbitals.
Build a Model of an Atom
This activity is good for explaining several concepts about atoms. This model follows the Niels Bohr model of an atom. You can make the framework for the model by tracing circles onto a clear placemat or cutting board. Whatever you use, it needs to be fairly thin. For beginning chemists, I recommend working with just two orbitals at first. The location of electrons in orbitals after the second orbital gets complicated, so keep it simple for beginners. Lay strips of double-sided tape in the middle of the circles. This will be the location of the nucleus of the atom.
Have your child or children take a look at the periodic table (I really like this placemat version because of its durability). Notice the atomic number above the name of each of the elements.
The atomic number tells you how many protons are in the nucleus of the atom. This is an atom’s identity. No other kind of atom will have that number of protons. For example, any atom that has just one proton is hydrogen. The atomic number for hydrogen is 1. Select an atom (choose one with an atomic number of ten or less since we are only dealing with two orbitals). Look at its atomic number. For our example we will use carbon. Carbon has an atomic number of 6 which means it has 6 protons in its nucleus. Take 6 tokens labeled with + (I used bingo tokens for this) and stick them to the double stick tape in the center of your atom (if you want to get fancy you can also use removable poster dots to stick your protons on).
Usually, there are about the same number of neutrons as protons in an atom. Carbon has 6 neutrons, so place 6 tokens labeled with 0 in the nucleus of the atom.
An atom in its neutral form will have the same number of electrons as protons. So carbon has six electrons, which we will represent with tiny magnets labeled with a minus sign. The tiny magnets are to remind us that electrons are much smaller than protons and neutrons. Place a second magnet underneath the mat behind each “electron” magnet to hold the “electrons” on. Younger children (6-7 or younger) might have a hard time manipulating the tiny magnets, so if you are working with younger children I recommend using brads instead of magnets. You will have to make some holes in your orbitals so you can stick the brads through.
Now its time to talk about orbitals! The first orbital can only hold two electrons. The second orbital can hold eight electrons. The inner orbital has to be filled before any electrons can go to the second orbital. The outer orbital of an atom is called its valence shell. Atoms are kind of particular in the way they like their valence shell to be. They are kind of all-or-nothing characters - they either like their valence shell to be completely full or completely empty. And they will give away, receive, or share electrons in order to get their valence shell closer to full or empty, which is how atoms bond together. We can show this by building two different atoms and “bonding” them together with our magnet or brad electrons.
Here we have carbon and oxygen. When they bond, they share 6 electrons in order to achieve a full eight electrons in their valence shells. This is called a covalent bond (co for together (sharing) and valent for valence electrons).
You can also use this model to represent an ionic bond. In an ionic bond, an atom donates an electron to another atom, creating one atom with a positive charge (the electron donor) and one atom with a negative charge (the atom that received the extra electron). The atoms have become ions, and because they are now charged they are attracted to each other. You can demonstrate this with a sodium fluoride molecule. Sodium (Na) has 11 electrons, and fluorine (F) has 9 electrons, so sodium gives one electron to fluorine giving them both a valence shell with eight electrons, which makes the valence shell full and the atoms happy!
Build sodium and fluorine and move one “electron” magnet from sodium to fluorine. Sodium is now positive because it has more positive protons than negative electrons, and fluorine has become a negative ion (fluoride) because it now has more negatively charged electrons than positively charged protons. Like magnets, the oppositely charged atoms are attracted to each other and bond together to form a molecule of sodium fluoride (NaF).
I did these activities with my own children (ages 6-12) and a group of homeschool children in that same range, and I was really impressed with how much information about atoms they were able to understand and retain. I hope your children enjoy these activities too!