Answer: An element with an atomic number of 20 has a higher atomic weight than an element with an atomic number of 10 for two main reasons:
Step-by-step explanation:
1. The number of protons in the nucleus of an atom determines the atomic number, while the sum of the protons and neutrons in the nucleus determines the atomic weight. Since an element with an atomic number of 20 has more protons and neutrons in its nucleus than an element with an atomic number of 10, it will have a higher atomic weight.
2. Elements with higher atomic numbers generally have more complex atomic structures and electron configurations, which can contribute to their higher atomic weights. In particular, the higher atomic number element may have more electron shells or subshells, which require more energy to hold the electrons in place, resulting in a higher overall mass for the atom.