A What an excellent question! I have wondered this myself as well. Perhaps you have already learned about the fact that atoms are composed of even smaller sub-atomic particles known as protons, neutrons, and electrons. You can technically divide these sub-atomic particles further into quarks, but that delves more into particle physics.

Protons, neutrons, and electrons are fundamental particles for matter, and a proton in gold is the same as it is in hydrogen, but gold and hydrogen are very different from each other. Why is this so? One way to look at it is at the atomic scale...

When we are first taught about atoms, we typically think of this picture, in which the protons, neutrons, and electrons are hard spheres (and the atom is sometimes portrayed in this manner, too!). This is not entirely wrong; it is still useful for counting how many electrons belong in each shell and showing the basic structure of an atom, but it's definitely not physically accurate.

The key takeaway is that even though all matter is composed of some combination of protons, neutrons, and electrons, each combination results in a whole variety of possible interactions between these sub-atomic particles. I'm going to focus mostly on interactions between electrons because they are responsible for a huge number of what we observe on the macroscopic scale, but there is a whole field of study dedicated to how the nucleus (composed of neutrons and protons) behaves, known as nuclear physics.

In schematics of atoms, electrons are typically shown as hard spheres. In reality, electrons are much more complicated. The second key takeaway is that you cannot capture all the physics behind an electron with the analogy of it orbiting a central body (i.e., the nucleus) like a planet. This is where quantum mechanics comes in, and because the electron is a quantum mechanical object, lots of weird (and unexpected!) phenomena arise.

First is that electrons (probabilistically, because of quantum mechanics!) occupy space around nucleus in a very unexpected way. They fill space according to orbitals (that can derived from quantum mechanics!). What do these orbitals look like? Click here to see!

As you can see, there is a set of orbitals that look like spheres, which is what you would kind of expect at first (i.e., there is an equal probability of finding an electron anywhere within some radius of the nucleus). But there are also orbitals that look like lobes and clovers, and even more complicated shapes that are directionally dependent. That is, you might see the electron more in one direction than in the other, and this can make a big difference in materials! These orbitals are associated with a particular energy of filling. Additionally, electrons follow a particular set of rules (e.g., Pauli exclusion principle that states no two identical electrons of the same spin can occupy the same state) for how they will fill these atomic orbitals. In combination, these two behaviors give us the richness of material properties that we see.

The above picture, however, only really tells you about how an electron fills space around an isolated atom. Materials are composed of many, many atoms! But it is how these electrons fill the atomic orbitals that also gives rise to the different types of bonding, which in turn results in very different material properties.

Why is this? Let's take an example of sodium (Na). Sodium is a metal. This means it conducts heat and electricity well; it also means that its very ductile and malleable. What makes sodium a metal is the fact that it has a single nearly free valence electron in its outer most atomic orbital. When you fill electrons in the orbitals, there is an energy associated with that particular configuration of filling. The lowest and most stable configuration is a half-filled or completely filled orbital. For sodium, it almost has a completely filled band, apart from that single nearly free valance electron, which is loosely bound to a nucleus that is shielded by all the other electrons filling the orbitals of lower energy. It is this nearly free electron that gives rise to the metallic bonding and thus metallic properties of sodium.

The story is different with sodium chloride (aka table salt, NaCl). NaCl is hard, brittle, and not a good conductor of heat or electricity- quite the opposite of metallic sodium! What happened? It has to do with the filling of electrons in atomic orbitals. Atoms are always looking for a half-filled or completely filled orbitals because it is more stable. Chlorine (Cl) almost has a filled orbital shell; it is off by one, which can be given by sodium! When sodium donates its electron, you form ions that are electrostatically attracted and form a strong bond, which is what makes salt so brittle.

Interactions between electrons themselves also result in interesting behavior. For instance, electron-electron interaction have been found be strong enough in some materials to result in an insulating properties when it is expected to be metallic ,read more about these Mott insulators here . In fact, whole areas of research are dedicated to understanding electron-electron interactions, including the one I am in!

That is a wonderful question!. It turns out that there are over 100 elements. Each element has a different size and a different number of electrons. Some elements also lose electrons more easily than others (when an atom loses electrons or gets extras we call it an ion). These properties change how the elements interact with each other.For example, minerals can only have certain elements in them, because only atoms/ions with the right size and number of electrons the will fit into the crystal. The structure of the mineral (how the atoms/ions are bonded) controls things like how the minerals break and the elements in the mineral control things like color.

Minerals like graphite are made of sheets of atoms, so they break easily into small flakes, which is why we use it in pencils. Minerals like quartz have a framework of ions so it does not have a preferred breaking direction and shatters into rough blocks. Liquids are made of molecules or atoms that are close together, but have little or no structure (they are not bonded together strongly like in minerals), so we can change the shape of a liquid easily. Gases are made of molecules or atoms that have no structure and are not close together, so they are even less organized than liquids, so we can change the shape and size of gases.

I hope that this has been helpful!

Looking at the periodic table of elements, there are about 114 different kinds of atoms (90 of them occur naturally, the others are produced synthetically). The properties of an atom though, do not necessarily determine the properties of the larger material. For instance, diamond (like used in jewelry) is incredibly hard, clear, and shiny and is made up entirely of carbon atoms. Graphite (like in your pencils) is soft, flaky, and grey, and is also entirely made up of carbon atoms. The difference is the way in which the atoms are connected and their arrangement.

Things can get even more complicated though when you start bonding different atoms together to form compounds. For instance, almost every living thing, and every material in those things is made up of molecules containing mostly carbon, hydrogen, and oxygen.

We typically group materials into broad classes to help understand how they gain their particular properties. For instance, metals are typically larger atoms (titanium = 22 protons, iron = 26 protons, lead = 82 protons) which are arranged in very specific arrangements. Salts (like table salt) are typically made from one atom on the left side of the periodic table and one on the right side (table salt is sodium chloride NaCl). This leads to materials that dissolve in water. Polymers (plastics) are made from carbon and hydrogen, in really long chains, which leads to them being bendable, elastic, and melt easily.

The study of how small scale atomic/molecular properties translates to larger scale properties such as appearance or feel is a very broad field called materials science. It is a combination of chemistry, physics, and engineering.

So everything in the universe is made of atoms, but not the same type of atoms. There are over 100 different types of atoms, though only about a couple dozen of those are common. For example, humans are made mostly of hydrogen, oxygen, nitrogen, and carbon. An important aspect of this is the way different types of atoms associate with each other. Metal atoms will often exist in a “sea” of atoms which gives metals their ability to be bent and shaped easily. Many nonmetal atoms however form little units called compounds in which one atom is combined with a different type of atom. The most common examples of this is when two hydrogen atoms combine with an oxygen atom, you get water. So, although everything in the universe is made of atoms, it is the different combinations of different atoms in different forms that make things in the universe feel and look different.

This is a good question! Ultimately, the answer boils down to the fact that different elements have different properties because they have different numbers of electrons. Having different numbers of electrons dictates what kinds of compounds atoms of an element will form, and consequently the physical properties (shape, color, texture, smell, etc.) of the compounds.

Atoms themselves are very different and may have very different properties. Think of how different things like iron or helium gas or diamond are. Each of these things is only made of a single atom (iron, helium, or carbon) but because the atoms themselves are very different, they may have very different properties. A good example of this is Legos. Lego blocks are all plastic but individually they may differ quite a bit (how many connections they make, shape, size, how they connect with other blocks). Similarly, the ways atoms come together affects the way things are. Think of baking. There are many ways to combine flour and water and salt etc., but you can get cakes or breads or cookies depending on the order you mix the ingredients, how much of each you use, and how you bake it, you can get very different results. It's cool, but still very hard to understand.

Well, not quite everything in the universe is made of atoms, but everything that you're familiar with (apart from light) is.

Atoms join together to form molecules, and those molecules have very different characteristics depending on what kind of atoms make them up and how the atoms are packed. Think for example about a pile of sand versus a sheet of glass: they're made of the same material, but they feel very different because of the different way that the material is put together - and they're made from the exact same atoms (two atoms of oxygen for every atom of silicon).