ScienceVerseLearning path: Elements
The concepts to learn before Elements, in order. Each step links to its page and, where one exists, its quiz.
Sign in to see which steps you have already opened and which quizzes you have completed.
Your path
- AtomsDirect prerequisite
An atom is the smallest unit of an element that keeps that element's chemical identity. Every atom has a tiny, dense nucleus of protons and neutrons, which holds nearly all of its mass, surrounded by electrons that fill almost all of its volume. The number of protons fixes which element the atom is; changing the number of electrons makes an ion, and changing the number of neutrons makes a different isotope.
- ElementsYour goal
A chemical element is a substance made of atoms that all have the same number of protons — the atomic number. Carbon is every atom with 6 protons, oxygen every atom with 8. Atoms of one element can differ in their number of neutrons (isotopes), which is why an element's listed atomic mass is a weighted average rather than a whole number. 118 elements are known; 94 occur naturally on Earth.
Where to go next
Concepts that build directly on Elements:
- Periodic Table: The periodic table lists every known element in order of atomic number, in 7 rows (periods) and 18 columns (groups). Elements in the same group have similar outer-electron arrangements and so behave in similar ways, which lets chemists predict properties from position. Mendeleev's 1869 version was so successful that it predicted elements nobody had yet found; the seventh period was completed in 2015.