For example, a helium atom has an atomic mass of 4, but an atomic number (or positive charge) of 2. Since electrons have almost no mass, it seemed that something besides the protons in the nucleus ...

rather than its atomic mass. Here are some popular mnemonics to help you remember the first 20 elements of the periodic table: H - Hydrogen He - Helium Li - Lithium Be - Beryllium ...

The relative atomic masses of elements are proportional measures. For example, the Ar for helium is 4.0, and the A r for carbon is 12.0. This means that carbon atoms have three times the mass of ...

And generations of children have sung the words, "hydrogen and helium, lithium ... mainly by their atomic mass. Although he wasn't the first to do this, his interpretation involved a leap of ...

The relative mass of a nucleus is the number of protons ... The relative charge of a nucleus is the same as its proton (atomic) number. Key fact: isotopes are forms of an element that have the ...