The atomic number of an element corresponds to the number of protons in the nucleus of an atom. To calculate the mass of an atom from its atomic number and symbol, you need to consider both the protons and neutrons in the nucleus.
Find the atomic number: The atomic number is usually written as a subscript to the left of the symbol of the element. It represents the number of protons in the atom. For example, the atomic number of carbon (C) is 6.
Determine the symbol of the element: The symbol represents the chemical abbreviation for the element. For example, the symbol for carbon is C.
Look up the atomic mass: The atomic mass of an element is usually written as a superscript to the left of the symbol or as a decimal number below the symbol. It represents the average mass of all the naturally occurring isotopes of that element. For example, the atomic mass of carbon is approximately 12.01.
Calculate the mass number: The mass number represents the total number of protons and neutrons in the atom. To determine the number of neutrons, subtract the atomic number (number of protons) from the mass number. For example, if the mass number of carbon is 12, then the number of neutrons would be 12 - 6 = 6.
Therefore, to calculate the mass of an atom from its atomic number and symbol, you can combine the atomic number (number of protons) with the number of neutrons. Keep in mind that the atomic mass on the periodic table represents the average mass of all the isotopes, so it may not always be a whole number.