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 mass number is the number of protons added to the number of neutrons. Hydrogen only contains 1 proton and no neutrons, so that gives a mass number of 1. However, there are some isotopes of Hydrogen, in other words, some atoms that have more than zero neutrons. For example, Deuterium has 1 neutrons hence an atomic mass of 2 and Tritium has 2 neutrons hence an atomic mass of 3. The number you see for atomic mass in a periodic table is an average of the abundance of the isotopes, which is why it's a decimal like 1.007941.00794 and not a whole number.