Explain how you can determine the number of neutrons in an atom
# protons = atomic number--that whole number usually in bold black print on the periodic table.
# protons + # neutrons = mass number--that isn't on the periodic table but usually is in the problem.
#p + #n = mass # and rearrange to
For example, 17Cl35 is chlorine with 17 protons and a total of 35 nucleons.(35 nucleons is another way of saying the mass number is 35)
35-17 = 18 neutrons.
#n = mass # - #p
To determine the number of neutrons in an atom, you need to know the atomic mass and atomic number of the element. Here's how you can find the number of neutrons in an atom using these two pieces of information:
1. Atomic number: The atomic number of an element represents the number of protons in its nucleus. You can find the atomic number of an element by referring to the periodic table. It is usually represented by the letter "Z."
2. Atomic mass: The atomic mass of an element represents the combined mass of its protons and neutrons. Also known as the mass number, it is usually represented by the letter "A." The atomic mass can also be found on the periodic table.
To determine the number of neutrons:
Step 1: Subtract the atomic number from the atomic mass.
Number of neutrons = Atomic mass - Atomic number
For example, let's consider the element chlorine (Cl) with an atomic number of 17 and an atomic mass of 35.45. By subtracting the atomic number from the atomic mass, we can calculate the number of neutrons:
Number of neutrons = 35.45 - 17
Number of neutrons = 18.45
Therefore, chlorine has 18.45 neutrons.
Note: The atomic mass on the periodic table is usually an average of all the naturally occurring isotopes of an element, which may have different masses due to varying numbers of neutrons. Hence, the atomic mass is often a decimal number.