How does the atomic mass determine the density of materials? Density of Copper The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element. For 63Cu, the atomic mass is less than 63, so this must be the dominant factor. A nucleus with greater binding energy has lower total energy, and therefore a lower mass according to Einstein’s mass-energy equivalence relation E = mc 2.
The nuclear binding energy varies between nuclei. This increases the mass of nuclei with more neutrons than protons relative to the atomic mass unit scale based on 12C with equal numbers of protons and neutrons. The neutron is slightly heavier than the proton. There are two reasons for the difference between mass number and isotopic mass, known as the mass defect: For example, 63Cu (29 protons and 34 neutrons) has a mass number of 63, and an isotopic mass in its nuclear ground state is 62.91367 u. For other isotopes, the isotopic mass usually differs and is usually within 0.1 u of the mass number. One unified atomic mass unit is approximately the mass of one nucleon (either a single proton or neutron) and is numerically equivalent to 1 g/mol.įor 12C, the atomic mass is exactly 12u, since the atomic mass unit is defined from it. One atomic mass unit is equal to 1.66 x 10 -24 grams. The unit of measure for mass is the atomic mass unit (amu). Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance. Note that each element may contain more isotopes. How does the atomic number determine the chemical behavior of atoms? Atomic Mass of Copper Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements. Copper is a chemical element with atomic number 29 which means there are 29 protons and 29 electrons in the atomic structure.
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