Atoms are often considered to be the building blocks of matter because they are the smallest units of chemical elements. These 10 atom facts cover basic information about atoms and some fun facts as well.
- The word atom comes from the Greek word atomos, which means “undivided” or “uncut.” The Greek philosopher Democritus coined the term in the 5th century BCE. Democritus believed atoms were units of matter that could not be cut into smaller pieces. Atoms became the fundamental units of matter and the building blocks of elements. Eventually, scientists learned about subatomic particles. While no chemical process can divide an atom, nuclear fission and decay can break them into smaller units.
- Atoms consist of protons, neutrons, and electrons. Protons have a positive electrical charge. Neutrons have no net electrical charge. Electrons have a negative electrical charge equal yet opposite to that of protons. Protons and neutrons have about the same mass as each other and form the atomic nucleus. Electrons are much smaller than protons or neutrons and orbit around the nucleus.
- The number of protons in an atom determines which element it is. For example, all atoms with 1 proton are hydrogen, while all atoms with 5 protons are boron. Most atoms also have electrons and neutrons, but the most common form of hydrogen has no neutrons and often loses its electron! Atoms of an element that have different numbers of neutrons are called isotopes. Changing the number of electrons forms different ions. Matter can consist of one type of atom (pure element) or the atoms can form bonds with each other to make compounds.
- At present, there are 118 different atoms. These correspond to the 118 elements of the periodic table. Around 92 of these elements occur in nature, while the rest are made in laboratories. The first synthetic atom was technetium, which has 43 protons. In the future, new atoms may be made by adding protons to existing atoms. These atoms will be radioactive and will quickly break apart or decay into smaller, more stable elements.
- Matter may feel solid, but it’s mostly empty space! This is because most of the volume of an atom is empty. The atomic nucleus is very dense and accounts for nearly all of an atom’s mass. It take 1,836 electrons to equal the mass of a single proton, so electrons don’t add much mass. The electrons orbit so far away from the nucleus that the atom is 99.9% space. To put it into perspective, if the atomic nucleus was the size of a pea, the atom would be the size of a sports arena.
- Atoms are very small. They cannot be seen with ordinary microscopes, although atomic force microscopy can visualize them. The radius of the average atom ranges from 30 picometers to 300 picometers, where a picometer is a trillionth of a meter. The radius of the average atom is less than 1/1000th the wavelength of visible light. The largest atom is cesium. It is about nine times larger than the smallest atom, which is helium.
- Three forces hold atoms together: electrical attraction, the strong force, and the weak force. Electrical attraction causes negative electrons and positive protons to be attracted to each other. It also makes electrons repel each other and protons repel each other. Even though protons repel each other, the strong and weak nuclear forces bind them to each other and to neutrons. The strong force is 1,038 times more powerful than gravity, but it only acts when particles are very close to each other.
- While no chemical means can divide an atom, they consist of even smaller particles than protons, neutrons, and electrons. They are made of subatomic particles called quarks and leptons. An electron is a type of lepton. Protons and neutrons each consists of three quarks.
- The most abundant type of atom is the universe is the hydrogen atom. About 74% of all the atoms in the Milky Way galaxy are hydrogen atoms.
- The human body contains about 7 billion billion billion atoms. Even though this is a vast number, about 98% of these atoms are replaced every year!
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