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Chapter 3: Problem 61

Explain why different atoms of the same element always have the same atomic number but can have different mass numbers.

Short Answer

Expert verified
Different atoms of the same element always have the same atomic number because the atomic number is determined by the number of protons, which doesn't change. These atoms can have different mass numbers because the mass number is the sum of protons and neutrons. Neutrons can vary in number, even among atoms of the same element, creating different isotopes.

Step by step solution

01

Defining Atomic Number

Define the atomic number. The atomic number is the number of protons in an atom. Protons have a positive charge and their number in the nucleus of the atom determines the identity of the atom. For instance, carbon atoms always have 6 protons, therefore, the atomic number of carbon is 6.
02

Defining Mass Number

Define the mass number. The mass number of an atom is the sum of neutrons and protons in the atom's nucleus. Neutrons are neutral particles in the nucleus and may vary in number even among atoms of the same element. This variation of neutron number is what leads to isotopes.
03

Comparing Atomic and Mass Numbers

To answer the original question, different atoms of the same element always have the same atomic number because the number of protons doesn't change. If the proton number changes, it's no longer the same element. On the other hand, these atoms can have different mass numbers because the number of neutrons in the atoms can vary. This creates isotopes of that element.

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