First, let's define what a molecule is. A molecule is a group of atoms that are connected by chemical bonds. The smallest molecule is the hydrogen molecule, H₂, which is made up of two hydrogen atoms (H) bonded to each other. These bonds are strong enough that the molecule usually stays in one piece even when other molecules are constantly bumping into it. For example, in the air, there are many nitrogen molecules (N₂) and oxygen molecules (O₂) constantly bumping into each other, but normally, they just bounce off each other.

Molecules are made by chemical reactions between atoms and/or molecules. These chemical reactions cannot create atoms--they just make new groups of atoms by breaking chemical bonds and making new ones. Usually, it costs energy to start a chemical reaction. For example, we can make hydrogen gas (H₂) and oxygen (O₂) react by mixing them together and heating them (heat is the energy cost). The mixture will react by taking groups of two H₂ molecules and one O₂ molecule, breaking their bonds, and reconnecting them into two water (H₂O) molecules. We usually write this reaction as the equation,

Notice that we end up with the same number of hydrogen atoms that we started with (four), and the same number of oxygen atoms (two). So even though this reaction made new water molecules, it did not make any new atoms. This is true for every chemical reaction!

Molecules are held together by chemical bonds. Those chemical bonds are made by sharing or exchanging electrons. You might have experienced a common example of this- oxygen! Oxygen molecules readily share their electrons which is why two oxygen atoms come together so easily to make up part of the air that we breathe!

Molecules are really tiny, but they are made up of even smaller things called atoms. Everything—plants and animals, rocks and metals, and more—is a collection of tiny atoms.

You can think of atoms as Lego. When you build with Lego, you combine small pieces into bigger creations, just like when atoms come together to make molecules. When atoms combine, the process is called a chemical reaction. And, just like you can join two Lego creations together, two or more molecules can come together to form a larger molecule. This is also called a chemical reaction.

A scientist who studies chemical reactions is called a chemist. Chemists play with atoms and molecules to form new molecules just like building with Lego!

Molecules are made in lots of different ways. Sometimes you can mix 2 different kinds of chemical molecules together and get new molecules. That's what happens when you mix vinegar and baking soda. Vinegar has acetic acid molecules. Baking soda has sodium bicarbonate. When you mix them, you get carbon dioxide molecules and sodium acetate. The carbon dioxide molecules are very bubbly.

Plants and animals make lots of different molecules. Green plants are exciting, because they can use energy from sunlight to make sugar and other food molecules. Animals need to eat plants or other animals to get their food.

A molecule is the smallest component in a chemical compound. They are made up by different atoms. Take water as an example: more water means more water molecules. The smallest amount of water would be one single water molecule. One single water molecule is made up by two hydrogen atoms and one oxygen atoms. Those atoms are held together by chemical bonds in order to form the molecule.

Atoms form chemical bonds with each-other to create molecules. Different kinds of atoms form different kinds of bonds. This is because of the different number of protons (+ charge) and electrons (- charge) that atoms hold, and with the different energy levels that electrons in atoms can have. You'll learn more about how atoms "choose" later when you take chemistry in high school.

Molecules are made up of atoms that are held together by chemical bonds. Some atoms can bond together easily like oxygen and chlorine. However, there are some atoms that cannot bind easily like neon and argon.

Molecules are a group of two or more atoms that have bonded together by sharing their electrons. That might have been a little confusing, so let’s take a step back and really think about what that means. There are two main parts of an atom, the nucleus which is made up of protons and neutrons, and the electron cloud, which takes up space around the nucleus. The number of protons in the nucleus determine the identity of the atom (hydrogen has one proton while helium has two protons) and this number does not change.

Electrons, on the other hand, are freer to come and go from the atom, which is why they participate in bonding. When atoms bond, they share one or more of their electrons together, forming a tight link between the two atoms. Congratulations, you’ve formed a molecule! It is important to remember here that the nuclei of the two atoms do not interact. Molecules allow a nearly unlimited different combinations of atoms to combine and form everything in our world. Thank you so much for the question!