Write the symbol for every chemical element that has atomic number greater than 55 and atomic mass less than 144.0 u
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The symbol :
There are two components that accompany an element, the mass number and atomic number
Atoms are composed of 3 types of basic particles (subatomic particles): <em>protons, electrons, and neutrons </em>
The Atomic Number (Z) indicates the number of protons and electrons in an atom of an element.
Atomic number = number of protons = number of electrons ⇒ neutral number
Atomic mass is the sum of protons and neutrons
Atomic Number (Z) = Atomic mass (A) - Number of Neutrons
The element has 71 electrons and a charge of +1 , so
Number of protons = 71 + 1 = 72
Number of protons = the atomic number = 72
The element with atomic number 72 is Hafnium(Hf)
The atomic mass of Hf = 178 g/mol