Which element has 38 protons in its nucleus?

• A. Yttrium (Y)
• B. Strontium (Sr)
• C. Zirconium (Zr)
• D. Rubidium (Rb)

Answer: (B)

Verified step by step guidance

1. Recall that the number of protons in the nucleus of an atom defines the atomic number of the element.
2. Identify the atomic numbers of the given elements: Yttrium (Y), Strontium (Sr), Zirconium (Zr), and Rubidium (Rb).
3. Use the periodic table to find the atomic number for each element. For example, Yttrium has atomic number 39, Strontium has atomic number 38, Zirconium has atomic number 40, and Rubidium has atomic number 37.
4. Compare the atomic numbers to the given number of protons (38) to determine which element matches.
5. Conclude that the element with 38 protons is the one whose atomic number is 38, which is Strontium (Sr).