Labh Lakshmi

Below is a list of all of the known elements, who they were discovered by and the year they were discovered. Some elements, such as gold, silver and iron, have been known since ancient times, so it is impossible to credit a single person for their discovery. Other elements were discovered around the same time by two or more scientists who were working independently of each other. In these cases, each scientist is listed along with the year they made their discovery. Other elements were discovered by teams of scientists working together. In cases like this, the known members of the team are listed along with a single year of discovery.

How many elements are there?

An element is a substance that is made entirely from one type of atom. For example, the element hydrogen is made from atoms containing a single proton and a single electron. If you change the number of protons an atom has, you change the type of element it is.

What are atoms made of?

Atoms are the basic building blocks of ordinary matter. Atoms can join together to form molecules, which in turn form most of the objects around you.

Atoms are composed of particles called protons, electrons and neutrons. Protons carry a positive electrical charge, electrons carry a negative electrical charge and neutrons carry no electrical charge at all. The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons ‘orbit’ the nucleus. A particular atom will have the same number of protons and electrons and most atoms have at least as many neutrons as protons.

Atoms are the smallest bits of ordinary matter and are made from particles called protons (which carry a positive electrical charge), neutrons (which carry no electrical charge) and electrons (which carry a negative electrical charge). The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons ‘orbit’ the nucleus. A particular atom will have the same number of protons and electrons and most atoms have at least as many neutrons as protons.

As fast as you can get them going! Well not quite. One of the facts of life discovered in the 20th century is that the speed of light (300,000 kilometers per second) is the ultimate speed limit. As you add energy to the electron, it will go faster, but as you get it to go close to the speed of light, you find that you have to add even more energy just to bump it a bit faster. For example, with just over 220,000 eV (which stands for a convenient unit of energy called the “electron-volt”), you can get the electron up to 90% of the speed of light. But to get it to 99.9% (just another 9.9%), you need a total of over 11 million eV! One way of looking at this is that the electron gets “heavier” (more massive) as it goes ever faster. So it’s harder to push it faster. At Jefferson Lab, a typical energy for the electrons in the beam is 4 GeV which is 4 billion eV. That means the electron is traveling at 99.9999992% of the speed of light. Close but still not 100%.