All practice pages/Interatomic theory
Seven elements never show up alone in nature. Learn which ones and how to write them, then quiz yourself until the list is automatic.
Seven elements are never found as single atoms in nature. A lone atom of any of them is short of a full outer shell, so it pairs with another atom of the same element and the two share electrons. That is why hydrogen gas is H₂, not H, and why “oxygen” in a reaction is written O₂. Every other element in its elemental form is written as a plain symbol: Na, He, Fe, C.
Six of the seven draw a 7 on the periodic table: nitrogen, oxygen, fluorine across period 2, then fluorine, chlorine, bromine, iodine straight down group 17. Hydrogen is the seventh, alone in the top corner.
Tap a formula to read about the molecule, or a name to read about the element. The seven cells on the map open the element pages too.
Five are gases at room temperature. Bromine is one of only two elements that are liquid at room temperature (mercury is the other), and iodine is a solid that goes straight to purple vapor when warmed. The molar mass of each molecule is twice the atomic mass, so use 70.90 g/mol for Cl₂, not 35.45.
Elemental goes into an equation as
Type each formula the way it goes in an equation, like Br2. The 2 turns into a subscript as you type. Order doesn’t matter.
Select every element below that is found in nature as a two-atom molecule. There might be none.
If you think none of them are diatomic, Check with nothing selected.