Analysis of a meteor shows the presence of the following stable isotopes of silicon: 28si (M=27.977 amu) - 67.0% 29si (M=28.976 amu) - 6.50% 30si (M=29.974 amu) - 26.5% Calculate the average atomic mass of silicon in this sample. Enter the value with the appropriate number of significant figures. amu

An element X bas five major isotopes, which are listed below along with their abundances. What is the element? Isotope Percent Natural Abundance Mass (u) 46x 8.00% 45.95232 47x 7.30% 46.951764 48x 73.80% 47.947947 49x 5.50% 48.947841 50x 5.40% 49.944792

A cube of sodium has length 1.25 in. How many atoms are in that cube? (Note: dNa=0.968 g/cm3.)

In Groups 4A-6A, there are several elements whose symbols begin with S. Name these elements, and for each one give its symbol, atomic number, group number, and period. Describe each as a metal, metalloid, or nonmetal.

Reference Section 5-2 to find the atomic masses of 12C and 13C, the relative abundance of 12C and 13C in natural carbon, and the average mass (in u) of a carbon atom. If you had a sample of natural carbon containing exactly 10,000 atoms, determine the number of 12C and 13C atoms present. What would be the average mass (in u) and the total mass (in u) of the carbon atoms in this 10,000-atom sample? If you had a sample of natural carbon containing 6.0221 1023 atoms, determine the number of 12C and 13C atoms present What would be the average mass (in u) and the total mass (in u) of this 6.0221 1023 atom sample? Given that 1 g = 6.0221 1023 u, what is the total mass of I mole of natural carbon in units of grams?

Click on the site (http://openstaxcollege.org/l/16PhetAtomMass) and select the Mix Isotopes tab, hide the Percent Composition and Average Atomic Mass boxes, and then select the element boron. Write the symbols of the isotopes of boron that are shown as naturally occurring in significant amounts. Predict the relative amounts (percentages) of these boron isotopes found in nature. Explain the reasoning behind your choice. Add isotopes to the black box to make a mixture that matches your prediction in (b). You may drag isotopes from their bins or click on More and then move the sliders to the appropriate amounts. Reveal the Percent Composition and Average Atomic Mass boxes. How well does your mixture match with your prediction? If necessary, adjust the isotope amounts to match your prediction. Select Nature’s mix of isotopes and compare it to your prediction. How well does your prediction compare with the naturally occurring mixture? Explain. If necessary, adjust your amounts to make them match Nature’s amounts as closely as possible. 21. Repeat Exercise 2.20 using an element that has three naturally occurring isotopes.

The mass spectrum of bromine (Br2) consists of three peaks with the following characteristics: Mass (u) Relative Size 157.84 0.2534 159.84 0.5000 161.84 0.2466 How do you interpret these data?

The following chart shows a general decline in abundance with increasing mass among the first 30 elements. The decline continues beyond zinc. Notice that the scale on the vertical axis is logarithmic, that is, it progresses in powers of 10. The abundance of nitrogen, for example, is 1/10,000 (1/104) of the abundance of hydrogen. All abundances are plotted as the number of atoms per 102 atoms of H. (The fact that the abundances of Li, Be, and B, as well as those of the elements near Fe, do not follow the general decline is a consequence of the way that elements are synthesized in stars.) (a) What is the most abundant main group metal? (b) What is the most abundant nonmetal? (c) What is the most abundant metalloid? (d) Which of the transition elements is most abundant? (e) Which halogens are included on this plot, and which is the most abundant?

The age of the universe is unknown, but some conclude from measuring Hubbles constant that the age is about 18 billion years old, which is about four times the age of Earth. If so, calculate the age of the universe in seconds. If you had a sample of carbon with the same number of carbon atoms as there have been seconds since the universe began, determine whether you could measure this sample on a laboratory balance that can detect masses as small as 0.1 mg.

The density of gold, Au, is 19.32 g/cm3. What is the volume (in cubic centimeters) of a piece of gold that contains 2.6 × 1024 atoms?