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1.- An aluminum ion, Al 3+ has: a) 13 protonsand 14 electrons b) 26p and 17e c)

ID: 75838 • Letter: 1

Question

1.- An aluminum ion, Al3+ has: a) 13 protonsand 14 electrons b) 26p and 17e c) 13p and 10e d) 26p and 23ee) 13p and 16 e 2.- Silicon, which makes up about 25% of Earth's crust bymass, is used widely in the modern electronics industry. It hasthree naturally ocurring isotopes, 28Si,29Si, 30Si. If the average atomic mass ofsilicon is 28.0855 amu, calculate the isotopic mass of29Si. Isotope                   IsotopicMass(amu)                                 Abundance(%) 28Si                            27.9769                                                         92.23 29Si                               ????                                                             4.67 30Si                             29.9738                                                          3.10 a)29.5452 amu b)28.4625 amu c)29.2252 amu d)28.0855 amu e)28.9765 amu 1.- An aluminum ion, Al3+ has: a) 13 protonsand 14 electrons b) 26p and 17e c) 13p and 10e d) 26p and 23ee) 13p and 16 e 2.- Silicon, which makes up about 25% of Earth's crust bymass, is used widely in the modern electronics industry. It hasthree naturally ocurring isotopes, 28Si,29Si, 30Si. If the average atomic mass ofsilicon is 28.0855 amu, calculate the isotopic mass of29Si. Isotope                   IsotopicMass(amu)                                 Abundance(%) 28Si                            27.9769                                                         92.23 29Si                               ????                                                             4.67 30Si                             29.9738                                                          3.10 a)29.5452 amu b)28.4625 amu c)29.2252 amu d)28.0855 amu e)28.9765 amu

Explanation / Answer

We Know that :    Al+3 has 13 protons and 10electrons. Average atomic mass = percentageabundance of the isotopes x Atomic mass of the element / Total abundance of the isotopes      28.0855   = 92.23 x 27.976 + 4.67 x M + 3.10 x 29.9738/ ( 92.23 + 4.67 + 3.10 )          M = 28.9765 amu   option e is correct.