Argon has three naturally occurring isotopes, with mass...

Argon has three naturally occurring isotopes, with mass numbers $36,38,$ and $40.$ a. Write the atomic symbol for each of these atoms. b. How are these isotopes alike? c. How are they different? d. Why is the atomic mass of argon listed on the periodic table not a whole number? e. Which isotope is the most prevalent in a sample of argon?

Argon has three naturally occurring isotopes, with mass numbers $36,38,$ and $40.$
a. Write the atomic symbol for each of these atoms.
b. How are these isotopes alike?
c. How are they different?
d. Why is the atomic mass of argon listed on the periodic table not a whole number?
e. Which isotope is the most prevalent in a sample of argon?

Key Concepts

Atomic Symbol Notation

Atomic symbols for isotopes include the element's symbol accompanied by its atomic number as a subscript and its mass number as a superscript. This notation succinctly conveys the number of protons (and electrons in a neutral atom) and the total number of nucleons (protons plus neutrons) in the nucleus.

Isotopes

Isotopes are variants of the same chemical element that have identical numbers of protons but different numbers of neutrons. This differences in neutron count lead to different mass numbers while the chemical properties remain nearly identical because they depend primarily on the number of protons and electrons.

Neutron Variation

The key difference among isotopes is the number of neutrons in the nucleus. Although the isotopes share the same atomic number, the variation in neutrons results in different mass numbers and can affect the isotopes' nuclear properties and stability.

Atomic Mass Weighted Average

The atomic mass listed on the periodic table is a weighted average of the masses of all naturally occurring isotopes of an element. Because this average takes into account the relative abundances of each isotope, it often results in a fractional number that does not match the mass number of any individual isotope.

Isotopic Abundance

Isotopic abundance refers to the relative proportions of different isotopes of an element found in nature. The most abundant isotope in a sample contributes the most to the weighted average atomic mass, even though several isotopes may be present.

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