For example, the atomic number of sodium is 11. Every sodium atom has 11 protons and 11 electrons. It has 11 positive charges and 11 negative charges. The mass number of an atom is its total ...

Scientists use the periodic table to quickly refer to information about an element, like atomic mass and chemical symbol. The periodic table’s arrangement ... the periodic table has evolved to reflect ...

25% of chlorine atoms are 37 Cl and 75% are 35 Cl. The weighted mean mass of chlorine is 35.5. The relative atomic mass of an element is a weighted mean mass of the isotopes of an element compared ...