Legs on a scorpion

Quarks in a proton

Pairs of chromosomes in a human somatic cell

Carbon atoms in a benzene ring

Faces on an icosahedron

Moons of Mars

Hypotenuse of a right triangle with legs measuring 7 and 24

Largest square number in the Fibonacci sequence

Nucleons in an alpha particle

Non-radioactive noble gases

Neutral pH

Sides on an undecagon

Only two-digit perfect number

Atomic number of uranium

Degrees equivalent to π/2 radians

Karats in pure gold

Digits in a googol, in base ten

Hardness of diamond on the Mohs scale

Bones in a normal human adult

Normal human body temperature, in degrees Celsius

Objects in the solar system that are more massive than Pluto

Specific gravity of water

Vertices on an icosahedron

Constellations recognized by the International Astronomical Union

Average human gestation period, in months

Six times nine, in base thirteen

Freezing point of water, in degrees Fahrenheit

Picometers in an angstrom

Carbon atoms in a buckminsterfullerene molecule

Divergence of a magnetic field, according to Gauss's law of magnetism

Boiling point of water, on the Réaumur scale

Base used in the hexadecimal system

Elements in the lanthanide series, including lanthanum itself

Interior angle of a regular pentagon, in degrees