Html viewer was selected to open .htm files and that would not handle mailto: and other links. This app reset that and then next time I opened the file it asked what app to use and I could select Browser (or Chrome). Perfect. At times, I want to use Chrome to open an .html file that I put on my tablet.
Neutrons have a mass of 1.675 Ã 10-24g, which is a little heavier than the proton. Neutrons are 1839 times heavier than electrons. Like all hadrons, neutrons are made of quarks. A neutron is made of two down quarks and one up quark. One up quark has a charge of +2/3, and the two down quarks each have a charge of -1/3.
The atomic mass for an atom of hydrogen is one dalton, which is calculated from the lone proton. Remember, electrons are too small to be considered in the atomic mass. Helium is the second lightest element, and is larger than hydrogen. It consists of two protons and two neutrons. Because protons and neutrons are approximately the same size, the atomic mass of a helium atom is four daltons. Let's look at a larger atom. Barium has an atomic mass of 137 daltons.