Chapter 2, Problem 2.92E

Early tables of atomic weights (masses) were generated by measuring the mass of a substance that reacts with 1.00 g of oxygen. Given the following data and taking the atomic mass of hydrogen as 1.00, generate a table of relative atomic masses for oxygen, sodium, and magnesium. Element Mass That Combines with 1.00g Oxygen Assumed Formula Hydrogen 0.126 g HO Sodium 2.875 g NaO Magnesium 1.500 g MgO How do your values compare with those in the periodic table? How do you account for any differences?

2.74 The accompanying table provides the identity of the two naturally occurring isotopes for four elements and the atomic weights for those elements. (In each case, the two isotopes differ in mass number by two.) Which element has the mass spectrum shown? Explain your answer.

Calculate the atomic mass of each of the following elements using the given data for the percentage abundance and mass of each isotope. a. Silver: 51.82% 107Ag (106.9 amu) and 48.18% 109Ag (108.9 amu) b. Silicon: 92.21% 28Si (27.98 amu), 4.70% 29Si (28.98 amu), and 3.09% 30Si (29.97 amu)

Give the complete symbol (XZA), including atomic number and mass number, of (a) a nickel atom with 31 neutrons, and (b) a tungsten atom with 110 neutrons.

Define mass number. What is the difference between mass number and atomic mass?

The mass-to-charge ratio for the positive ion F+ is 1.97 107 kg/C. Using the value of 1.602 1019 C for the charge on the ion, calculate the mass of the fluorine atom. (The mass of the electron is negligible compared with that of the ion, so the ion mass is essentially the atomic weight.)

The photo here depicts what happens when a coil of magnesium ribbon and a few calcium chips are placed in water. (a) Based on these observations, what might you expect to see when barium, another Croup 2A element, is placed in water? (b) Give the period in which each element (Mg. Ca, and Ba) is found. What correlation do you think you might find between the reactivity of these elements and their positions in the periodic table?

Chlorine has two isotopes, Cl-35 and Cl-37. Their abundances are 75.53% and 24.47%, respectively. Assume that the only hydrogen isotope present is H-1. (a) How many different HCI molecules are possible? (b) What is the sum of the mass numbers of the two atoms in each molecule? (c) Sketch the mass spectrum for HCI if all the positive ions are obtained by removing a single electron from an HCI molecule.

Mass spectrometric analysis showed that there are four isotopes of an unknown element having the following masses and abundances: Three elements in the periodic table that have atomic weights near these values are lanthanum (La), atomic number 57, atomic weight 138.9055; cerium (Ce), atomic number 58, atomic weight 140.115; and praseodymium (Pr), atomic number 59, atomic weight 140.9076. Using the data above, calculate the atomic weight, and identify the element if possible.