Sodium $(Na)$ has 11 protons and 12 neutrons. What is its isotope notation?
A. $Na -11$
B. $Na-12$
C. $Na -23$
D. $Na -34$
Answer (2)
Determine the mass number by adding the number of protons and neutrons: M a ss u mb er = 11 + 12 = 23 .
Represent the isotope notation as element symbol - mass number.
Write the isotope notation for Sodium as Na-23.
The isotope notation for Sodium is N a − 23 .
Explanation
Understanding the Problem We are given that Sodium (Na) has 11 protons and 12 neutrons. We need to determine its isotope notation. The isotope notation is represented as element symbol - mass number. The mass number is the sum of the number of protons and neutrons in the nucleus of an atom.
Calculating the Mass Number To find the mass number, we add the number of protons and neutrons: M a ss u mb er = N u mb er u mb ero f u mb er P ro t o n s + N u mb er u mb ero f u mb er N e u t ro n s M a ss u mb er = 11 + 12 M a ss u mb er = 23
Determining the Isotope Notation The isotope notation is the element symbol followed by a hyphen and the mass number. In this case, the element symbol for Sodium is Na, and the mass number is 23. Therefore, the isotope notation is Na-23.
Final Answer The isotope notation for Sodium is Na-23. Therefore, the correct answer is C.
Examples
Isotope notation is used in various fields, including chemistry, nuclear physics, and medicine. For example, in carbon dating, the isotope notation helps scientists determine the age of organic materials by analyzing the ratio of carbon-14 ( 14 C ) to carbon-12 ( 12 C ). In medicine, radioactive isotopes like iodine-131 ( 131 I ) are used in diagnostic imaging and cancer treatment. Understanding isotope notation is crucial for accurately representing and interpreting data in these applications.
The isotope notation for Sodium, which has 11 protons and 12 neutrons, is Na-23. This is calculated by adding the number of protons and neutrons to get a mass number of 23. Therefore, the correct answer is option C, Na-23.
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