I believe it is the percent abundance. Isotopes are atoms of the same element with similar atomic number but different mass number. Natural abundance is the abundance of isotopes of a chemical element as naturally found on the planet. The relative atomic mass of these isotopes is the atomic weight listed for the element in the periodic table.
Answer:
Alain Aspect, David Baltimore, Allen Bard, and Timothy Berners - Lee
Pressure difference = depth x density x gravity
<span>atoms are made of particles that have a negative charge.</span>
