Which element on the periodic table has 55 protons?

• A. Rubidium (Rb)
• B. Strontium (Sr)
• C. Barium (Ba)
• D. Cesium (Cs)

Answer: (D)

Verified step by step guidance

1. Recall that the number of protons in an atom is equal to its atomic number, which uniquely identifies each element on the periodic table.
2. Look up the atomic numbers of the given elements: Rubidium (Rb), Strontium (Sr), Barium (Ba), and Cesium (Cs).
3. Compare the atomic numbers to find which element has exactly 55 protons.
4. Identify that the element with atomic number 55 is Cesium (Cs).
5. Conclude that Cesium (Cs) is the element with 55 protons based on its atomic number.