Science quick reference
Constants and prefixes worth memorizing, and a periodic table cheat sheet for the basics.
Physical constants
| Constant | Symbol | Value |
|---|
| Speed of light (vacuum) | c | 2.998 × 10⁸⁺ m/s |
| Gravitational acceleration (Earth) | g | 9.81 m/s² |
| Avogadro's number | N₀ | 6.022 × 10²³ /mol |
| Planck's constant | h | 6.626 × 10⁻³⁴ J·s |
SI prefixes
| Prefix | Symbol | Factor |
|---|
| giga | G | 10⁹ |
| mega | M | 10⁾ |
| kilo | k | 10³ |
| centi | c | 10⁻² |
| milli | m | 10⁻³ |
| micro | µ | 10⁻⁵ |
| nano | n | 10⁻⁹ |
Periodic table basics
- Elements are ordered by atomic number (protons), not mass.
- Columns (groups) share valence electron count and similar chemistry.
- Rows (periods) share the number of electron shells.
- Metals sit left/center, nonmetals sit upper-right, metalloids form a diagonal border between them.
- Noble gases (rightmost column) are largely unreactive — full outer shell.