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.
An atom consists of a central nucleus surrounded by an electron cloud. The nucleus is a tightly packed ball made up of protons and neutrons. The mass of the proton and the neutron are nearly the same. The mass of the electron is about 1/2000 of that. The proton has a charge of +1. The neutron has a charge of 0. The electron has a charge of -1. The number of protons in the nucleus is called the atomic number. It tells us what the element is. Hydrogen has one proton, helium has two, lithium three, etc. The number of neutrons gives you the isotope of the given element.