Calcium atomic mass

E.3 In your new nanotechnology lab you have the capability to manipulate individual atoms. The atoms on the left are bromine atoms (molar mass 80 g-mol L), those on the right are atoms of calcium (molar mass 40 g-mol" 1). How many calcium atoms would have to be added to the pan on the right for the masses on the two pans to be equal ... 

One problem with Mendeleev s table was that some elements seemed to be out of place. For example, when argon was isolated, it did not seem to have the correct mass for its location. Its relative atomic mass of 40 is the same as that of calcium, but argon is an inert gas and calcium a reactive metal. Such anomalies led scientists to question the use of relative atomic mass as the basis for organizing the elements. When Henry Moseley examined x-ray spectra of the elements in the early twentieth century, he realized that he could infer the atomic number itself. It was soon discovered that elements fall into the uniformly repeating pattern of the periodic table if they are organized according to atomic number, rather than atomic mass. 

Fig. 3.42. Depletion below solar abundances of elements in the H I gas towards f Ophiuchi plotted against atomic mass number in (a) and condensation temperature in (b), based in part on the curve of growth shown in Fig. 3.11. Vertical boxes indicate error bars. The dotted curve in the left panel represents an A-1/2 dependence expected for non-equilibrium accretion of gas on to grains in the ISM. The condensation temperature gives a somewhat better, though not perfect, fit, suggesting condensation under near-equilibrium conditions at a variety of temperatures either in stellar ejecta or in some nebular environment. Note the extreme depletion of Ca ( Calcium in the plane stays mainly in the grain ). After Spitzer and Jenkins (1975). Copyright by Annual Reviews, Inc.

Example Calculate the mass of calcium oxide obtained when 20.0 g of calcium carbonate are thermally decomposed (relative atomic masses Ca = 40, C = 12, O = 16). 

Doubly-charged ions exist because the potential of second ionization of many metals is relatively low with respect to the plasma thermal energy. For instance, 11.9 eV are needed to remove two electrons, in contrast with 6.1 eV for one electron, from a calcium atom. At 8000K, a little less than 0.1% of Ca would be in the Ca + form and overlap with Mg+ isotopes. Likewise, Ba is rather easily formed and overlaps with Zn+ isotopes. Isobaric interferences with doubly-charged ions are easily identified as odd-mass atoms will produce peaks at half masses, such as Ca at mass 21.5. 

Q16 Calculate the weight in grams of 1 mole sulphate in calcium sulphate (relative atomic mass of calcium = 40.08 sulphur = 32.07 oxygen = 16.00) ... 

As the number of elements increased, so did attempts to organize them into meaningful relationships. Johann Dobereiner (1780-1849) discovered in 1829 that certain elements had atomic masses and properties that fell approximately mid-way between the masses and properties of two other elements. Dobereiner termed a set of three elements a triad. Thus, chlorine, bromine, and iodine form a triad Dobereiner proposed several other triads (lithium-sodium-potassium, calcium-strontium-barium). Dobereiner recognized that there was some sort of relationship between elements, but many elements did not fit in any triad group, and even those triads proposed displayed numerous inconsistencies. 

Calcium oxide crystallizes with a face-centred cubic lattice, a=481 pm and a density /)=3.35x10 kg m calculate a value for Z (Atomic masses of Ca and 0 are 40.08 and 15.999, respectively.)... 

One problem with Mendeleev s table was that some elements seemed to be out of place. For example, when argon was isolated, it did not seem to have the correct mass for its location. Its relative atomic mass of 40 is the same as calcium s, but argon is an inert gas and calcium a reactive metal. Such anom-... 

However, other scientists had also attempted to categorise the known elements. In 1817, Johann Dobereiner noticed that the atomic weight (now called atomic mass) of strontium fell midway between the weights of calcium and barium. These were elements which possessed similar chemical properties. They formed a triad of elements. Other triads were also discovered, composed of ... 

Heavy metal A metallic element with an atomic mass greater than that of calcium (40.08 atomic mass units) (Drever, 1997), 175. 

You know the formula of calcium phosphate. You also know, from the periodic table, the average atomic mass of each atom that makes up calcium phosphate. 

A 1.42-g sample of a pure compound, with formula M2S04, was dissolved in water and treated with an excess of aqueous calcium chloride, resulting in the precipitation of all the sulfate ions as calcium sulfate. The precipitate was collected, dried, and found to weigh 1.36 g. Determine the atomic mass of M and identify M. 

Calcium has a relative atomic mass of 40 how many moles are there in 10 g of calcium ... 

If the relative atomic masses of calcium, carbon and oxygen are 40, 12 and 16, respectively, what is the relative formula mass of calcium carbonate, CaCOs ... 

Relative atomic masses silver, 108 nitrogen, 14 oxygen, 16 carbon, 12 chlorine, 35.5 calcium, 40 sodium, 23. 

A graphing calculator can run a program that calculates the numbers of protons, electrons, and neutrons given the atomic mass and numbers for an atom. For example, given a calcium-40 atom, you will calculate the numbers of protons, electrons, and neutrons in the atom. 

Examine the ratio of atomic mass to atomic number for the elements with even atomic number through calcium. This ratio is approximately the ratio of the average mass number to the atomic number. 

Melting points for calcium, strontium, and barium show a similar trend. The average of the atomic masses of calcium and barium is about 88.5, which is close to 88, the actual atomic mass of strontium. However, the pattern of the boiling points in this triad is irregular. The irregular pattern of boiling points is typical of triads involving metals. 

What is the weighted average mass in atomic mass units (u) of each atom of the elements (a) calcium and (b) neon ... 

The formula, CaCl2, represents one formula unit of the compound and represents the simplest ratio of its ions. One mole of an ionic compound contains Avogadro s number of formula units of the compound, so instead of molecular mass, the term formula mass is used. The formula mass of CaCl2 is the sum of the atomic masses of all the atoms in its formula. The atomic masses of the calcium and chloride ions are the same as those of the neutral atoms. The formula mass of CaCl2, with 3 atoms in its formula, is as follows ... 

Note that although calcium and chlorine exist here as ions, the formula mass is the sum of the atomic masses. For this reason, calcium and chlorine are shown as atoms when adding the atomic masses of the ions. The formula mass in grams is the molar mass of CaCl2, 110.98 g. 

Example 2 Find the molar mass of Ca3(P04)2. Determining the formula mass of calcium phosphate, Ca3(P04)2, which has 3 calcium ions, Ca2+, and 2 phosphate ions, P043-, starts by counting the atoms of each element in the formula—3 Ca, 2 P, and 8 O—and ends by adding the atomic masses of the 13 atoms. 

With a few exceptions, Moseley found that atomic nnmber increases in the same order as atomic mass. For example, calcium is the twentieth element in order of increasing atomic mass, and it has an atomic nnmber of 20. The discrepancies that had puzzled earlier scientists now made sense. The atomic nnmber of argon is 18 and that of potassium is 19, so potassium should follow argon in the periodic table. 

Physical and Chemical Properties Strontium is a member of the alkaline earth elements, with atomic number 38 and atomic mass 87.62. It possesses four stable isotopes Sr (0.56%), Sr (9.86%), Sr (7.00%), and Sr (82.58%) (Emsley 1992). The pure metal strontium, while less reactive than the alkali metals, is a strong reducing agent and requires appropriate handling. Strontium reacts vigorously with water to form SrOH, liberating Hj in the process. In its chemical characteristics it resembles calcium and barium, and has properties intermediate between these two elements. The strontium atom easily loses two electrons in the 5 s level to form the divalent ion Sr " ". This ion occurs in many... 

Ans. The formula mass of calcium chloride (using rounded-off values of atomic masses) is 111.0. The mass of CaQ2 in 3.20 mol is... 

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