百度试题 结果1 题目6 An atom of element Q contains 19 electrons, 19 protons and 20 neutrons.What is Q? B A calcium B potassium C strontium D yttrium 相关知识点: 试题来源: 解析 B 反馈 收藏
ICSEC - Grade 09 - CHEMISTRY - Atomic Structure And Chemical Bonding - Q23
An atomic number of 1 means the atom is hydrogen, atomic number 2 means helium, 3 means lithium, 4 is beryllium, and so on. The total number of protons and neutrons added together is called the relative atomic mass. Hydrogen has a relative atomic mass of 1, while helium's relative ...
For12C, the atomic mass is exactly 12u since the atomic mass unit is defined from it. The isotopic mass usually differs for other isotopes and is usually within 0.1 u of the mass number. For example,63Cu(29 protons and 34 neutrons) has a mass number of 63, and an isotopic mass in ...
Theneutron isslightlyheavierthan theproton. This increases the mass of nuclei with more neutrons than protons relative to the atomic mass unit scale based on12C with equal numbers of protons and neutrons. Thenuclear binding energyvaries between nuclei. A nucleus with greater binding energy has lower...