# Chemistry explained

Each atom can be measured on a table, called [the Periodic Table of Elements](science-chemistry.png).

Electrons exist in certain layered orbits. The first 2 exist in a "shell", then the next 8, then the next 18, then 8. The outer shell's electrons are called valence electrons. Generally, some atoms (like copper, silver, and gold) transmit electrons better because of their relative valence electrons.

Because of valence electrons, certain patterns arise as atoms increase in atomic weight:

- Alkali metals (Lithium, sodium, potassium, rubidium, cesium, francium) - Group 1
  - They react *very* violently with water and create a strong base (alkali).
- Alkali earth metals (beryllium, magnesium, calcium, strontium, barium, radium) - Group 2
  - Like alkali metals, they react violently with water.
  - They can withstand heat, and exist naturally within the Earth's crust.
- Transition and inner transition metals group (Atomic numbers 21-30, 39-48, 57-80, 89-112) - Groups 3-12
  - They're called "transition" elements because they appear to transition from metallic (electrically positive) to non-metallic (electrically negative) as you move rightward.
  - Inner transition metals are broadly classified as Group 3 (3rd column) based on how they behave, so they all fit inside that group. They're also called "rare earth metals", and are extremely useful in making [batteries](engineering-electrical.md).
  - It's also worth noting that Group 3 (atomic numbers 57-71 and 89-103) are separated visually at the bottom, simply to save space and make it more aesthetically pleasing when printing it out on a standard sheet of paper.
- Boron/icosagen group (boron, aluminum, gallium, indium, thallium, nihonium) - Group 13
- Carbon group (carbon, silicon, germanium, tin, lead, flerovium) - Group 14
  - Tends to be very stable relative to the other elements.
- Nitrogen/pnictogen group (nitrogen, phosphorus, arsenic, antimony, bismuth, moscovium) - Group 15
- Oxygen/chalcogen group (oxygen, sulfur, selenium, tellurium, polonium, livermorium) - Group 16
  - Lower-rank chalcogens are often critical to maintain life, but higher-rank chalcogens are often toxic
- Halogen group (fluorine, chlorine, bromine, iodine, astatine, tennessine) - Group 17
  - When halogens react with metals, they tend to create salts (halogen literally means "salt maker")
  - The specific way they interact with other elements makes chlorine, bromine, and iodine excellent [disinfectants](home-housekeeping.md).
- Noble gases/aerogens group (helium, neon, argon, krypton, xenon, radon, oganesson) - Group 18
  - Because their valence electron shells are full, they tend to be *very* stable.
- Some elements (such as boron), are metalloids because they show properties of metals *and* non-metals at the same time.

Some atoms have too many or too few neutrons, even though they have the same number of protons and behave the same. These are called isotopes and are represented as a number afterward (e.g., a common uranium isotope is U-238 instead of having 237 neutrons). Their atomic mass is offset by the differing neutrons, and can be calculated proportionally to the composition of variously sized isotopes in a sample. An element's molecular ratio of its isotopes is easy to detect by observing how they respond to various wavelengths of light (also known as "spectroscopy").

The higher up the periodic table, the more complex the atom gets, and it *generally* becomes more unstable. Most of the highest atomic weight elements are either theoretical or were man-made for a fraction of a second before they disintegrated. New [technology](technology.md) is constantly making new particles, just to see if it's possible.

By combining atoms together, they can form bonds that create molecules. These molecules can often be more stable (or unstable) than their individual elements. Table salt, for example, is unbelievably stable, but is made of two highly unstable elements (sodium and chlorine).

When molecules interact, they're creating a reaction. That reaction will persist until nearly all the molecules have resolved their chemical differences. Other molecules, called catalysts, can interact with that mixture to speed up or slow down that process.

A mixture of different types of molecules together is a solution. In that sense, a Coca-Cola and a hamburger are both solutions. These chemicals tend to interact with each other in different ways, and this implements in various ways that range from [cleaning](home-housekeeping.md) to [cooking](cooking.md).

Water is a frequent molecule because of electron bonds. Essentially, oxygen (which has 4 electrons when not ionized) easily pairs with hydrogen ions (which use 1 electron when not ionized). Thus, unionized water is effectively 6 protons and 4 electrons, with the means to be easily ionized by picking up more electrons.

Because of water's ubiquity, hydrogen ions are frequently part of chemical reactions. The letter *p* in scientific calculations represents "-log10", so pH is an inverse measurement of how many hydrogen ions can get released from a chemical. Thus, a weak acid (like black coffee) will release some hydrogen ions, while a strong base (like chlorine bleach) won't release any. The difference in the releasing of hydrogen ions makes a *huge* difference in how much the chemicals react with one another.