Which of these elements is most reactive? -- I F Br Cl

A scientist is trying to discover information about an unknown metal in a compound. The formula for the compound is believed to be XBr, where X is the unknown metal. The scientist determined that a 4.720 g sample of this compound contains 4.745 x 10-2 mol Br. Calculate the atomic mass of the unknown metal, X. atomic mass = amu What is the identity of the metal? Provide the name or symbol of the element. metal:

K H 2A Li Be Na Mg 3B 4B 5B 6B 7B8B K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga 3A 4A 5A 6A 7A He F Ne Cl Ar BCN0 Si P Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In * Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Fr Ra Ac Rf Ha ** silicon, phosphorus, aluminum, sulfur 18 2B Al smallest largest 8A S Ge As Se Br Kr Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Sn Sb Te I Xe Arrange the following elements in order of increasing electronegativity: Pb Bi Po At Rn Please answer this question according to the general rules you have learned regarding periodic trends. DO NOT base your answer on tabulated values since exceptions may occur.

A 2.58 g sample of a compound consisting of carbon, hydrogen, oxygen, nitrogen, and sulfur was combusted in excess oxygen. This produced 2.79 g2.79 g CO2CO2 and 1.52 g1.52 g H2OH2O. A second sample of this compound with a mass of 4.57 g4.57 g produced 3.00 g3.00 g SO3SO3. A third sample of this compound with a mass of 8.79 g8.79 g produced 4.53 g4.53 g HNO3HNO3. Determine the empirical formula of the compound. Enter the correct subscripts on the given chemical formula