An atom is the smallest unit of ordinary matter that forms a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small, typically around 100 picometers across. They are so small that accurately predicting their behavior using classical physics—as if they were tennis balls, for example—is not possible due to quantum effects.
Atomic theory
Atomic theory is the scientific theory that matter is composed of particles called atoms. Atomic theory traces its origins to an ancient philosophical tradition known as atomism. According to this idea, if one were to take a lump of matter and cut it into
Time constraint
In law, time constraints are placed on certain actions and filings in the interest of speedy justice, and additionally to prevent the evasion of the ends of justice by waiting until a matter is moot. The penalty for violating a legislative or court
A proton is a subatomic particle, symbol p or p+, with a positive electric charge of +1e elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are jointly referred
Chemical element
In chemistry, an element is a pure substance consisting only of atoms that all have the same numbers of protons in their nuclei. Unlike chemical compounds, chemical elements cannot be broken down into simpler substances by any chemical reaction. The
Sundman (crater)
Sundman is a lunar impact crater that lies just past the western limb of the Moon. Although it lies on the far side from the Earth, this part of the surface is brought into view during periods of favorable libration and illumination. Sundman lies to the
Timeline of scientific experiments
The timeline below shows the date of publication of major scientific experiments
The 790s decade ran from January 1, 790, to December 31, 799
Principal quantum number
In quantum mechanics, the principal quantum number is one of four quantum numbers assigned to each electron in an atom to describe that electron's state. Its values are natural numbers making it a discrete variable
The 870s decade ran from January 1, 870, to December 31, 879
Erna Lesky
Erna Lesky was an Austrian pediatrician and historian of medicine. She was the first woman on the medical faculty of the University of Vienna, and was named as "one of the most illustrious medical historians of the twentieth century" by Owen Harding