If you don't know the relative atomic mass or mass number of an element, there are several ways you can find this information:
Periodic Table: The periodic table provides the atomic symbol and atomic number of each element. The atomic number corresponds to the number of protons in the nucleus, which is also the number of electrons in a neutral atom. The relative atomic mass (also known as atomic weight) is usually provided below the element's symbol. However, if the periodic table you're using doesn't display the atomic mass, you can use other methods to find it.
Online Resources: There are numerous online resources available that provide information on atomic masses. You can search for a specific element or consult websites that offer comprehensive periodic table data. Websites such as the National Institute of Standards and Technology (NIST) or reputable chemistry textbooks are reliable sources to find atomic masses.
Chemistry Reference Books: Physical or inorganic chemistry textbooks often contain comprehensive tables or appendixes that provide atomic masses for various elements. These books are valuable references for finding atomic masses and other relevant information.
Periodic Table Apps or Software: There are many mobile apps and computer software programs available that provide detailed information about elements, including their atomic masses. These tools are convenient and can be easily accessed to look up atomic masses.
It's important to note that atomic masses are usually given as average values since many elements have isotopes with different masses. The average atomic mass takes into account the relative abundance of each isotope. In some cases, atomic masses may also vary slightly depending on the source and the level of precision required.
By utilizing these resources, you should be able to find the atomic mass and other essential information for any element you need.