Electricity and Electrons

Pioneers of Electricity Dalton’s atomic model did not take electricity into account – a major limitation. What is the relationship, if any, between electricity and atoms? Tremendous advances took place harnessing electricity between 1750 and 1890, yet no one understood what it was.

Benjamin Franklin Studied electricity in the 1740’s First to use “+” and “-”when describing electricity it is now discovered and demonstrated, both here and in Europe, that the Electrical Fire is a real Element, or Species of Matter, not created by the Friction, but collected only. — Letter to Cadwallader Colden, 5 June 1747

Luigi Galvani (1771) Discovered that the muscles of dead frogs legs twitched when touched with a spark: called it “bioelectricity”

Alessandro Volta “father” of electrochemistry Invented battery in 1800

Batteries were used to do all sorts of things… 2012 global production of Cl2: 280,000,000 metric tons (9 lb/person/year)

Humphrey Davy Davy knew that electricity was related to matter, but how? Davy knew that molten salts conduct electricity (solids do not!) Used voltaic cells to discover elements Na, K, Mg, Ca, Sr, and Ba.

Davy’s Elements

Davy’s Accident While synthesizing nitrogen trichloride, Davy was temporarily blinded when it exploded. Davy was forced to hire a lab assistant, Michael Faraday, who later became one of the all-time great scientists.

Michael Faraday Faraday did some chemistry with Davy (discovering benzene among other things) He discovered the principles behind electric motors He discovered electromagnetic induction, which led to power generators and transformers First to use words like “electrode,” “cathode,” and “ion”

Early Uses of Electricity Faraday’s breakthroughs led to some fabulous inventions that changed humanity forever:

Cathode Ray Tubes One of the tools used back then (1870’s) was the discharge tube – a tube in which two metallic electrodes are sealed, and all air removed from the tube. A current is made to flow through the tube, and a glow appears at the negative end (cathode). This glow was thought to be some kind of invisible particles that came from the cathode. William Crookes (1870) showed that a magnet changes the direction of the glow.

Discovery of the Electron In 1897, JJ Thomson used a modified “Crookes Tube” to identify the particle that came to known as an electron.

Thomson’s Plum Pudding Model (1904)