Question

clue,element
this element is an alkali metal with 55 protons.,cs
this element is a noble gas with 86 protons in its nucleus.,rn
the atomic number of this element is 49.,in
this element has 2 fewer electrons than bromine (br).,as
this element has one more electron than indium (in).,sn
this element is directly below the element that has 34 protons in its nucleus,te
this newly synthesized element has 118 protons.,og
this element has 51 electrons surrounding its nucleus.,sb
this element has 6 electrons surrounding its nucleus.,cs
this element directly below the element whose atomic number is 81.,pb
this element has 81 electrons surrounding its nucleus.,tl
the atomic number of this element is 15.,p
this element has 4 more protons than thallium (tl) in its nucleus.,at
this element has 1 less proton than polonium (po) in its nucleus.,bi

Explanation:

Step1: Recall element - proton/electron relationship

In a neutral atom, the number of protons = atomic number = number of electrons.

Step2: Analyze each clue

• "This element is an alkali metal with 55 protons": The atomic number is 55, and the element is Cesium (Cs).
• "This element is a noble gas with 86 protons in its nucleus": The atomic number is 86, and the element is Radon (Rn).
• "The atomic number of this element is 49": The element is Indium (In).
• "This element has 2 fewer electrons than Bromine (Br)": Bromine has 35 electrons, so this element has 33 electrons and 33 protons, which is Arsenic (As).
• "This element has one - more electron than Indium (In)": Indium has 49 electrons, so this element has 50 electrons and 50 protons, which is Tin (Sn).
• "This element is directly below the element that has 34 protons in its nucleus": The element with 34 protons is Selenium (Se), and the element below it in the same group is Tellurium (Te).
• "This newly synthesized element has 118 protons": The element is Oganesson (Og).
• "This element has 51 electrons surrounding its nucleus": So it has 51 protons, and the element is Antimony (Sb).
• "This element has 6 electrons surrounding its nucleus": So it has 6 protons, and the element is Carbon (not Cs as given wrongly in the table for this clue).
• "This element directly below the element whose atomic number is 81": The element with atomic number 81 is Thallium (Tl), and the element below it is Lead (Pb).
• "This element has 81 electrons surrounding its nucleus": So it has 81 protons, and the element is Thallium (Tl).
• "The atomic number of this element is 15": The element is Phosphorus (P).
• "This element has 4 more protons than Thallium (Tl) in its nucleus": Thallium has 81 protons, so this element has 85 protons, which is Astatine (At).
• "This element has 1 less proton than Polonium (Po) in its nucleus": Polonium has 84 protons, so this element has 83 protons, which is Bismuth (Bi).

Answer:

The elements corresponding to the clues are: Cs, Rn, In, As, Sn, Te, Og, Sb, C (not Cs as in table), Pb, Tl, P, At, Bi