The atomic number of calcium (Ca) is 20, and it's mass number is 40. What is true about the subatomic particles that make up a neutral atom of calcium? A) It has 20 protons, 20 neutrons and 20 electrons. B) the total number of subatomic particles in Ca is 40. C) The number of electrons cannot be determined from the information given. The atomic number of calcium (Ca) is 20.The atomic weight of Ca is 40.078 grams per mole.See the Web Links and the Related Questions to the left of this answer for a periodic table and more. Calcium is an element with atomic symbol Ca, atomic number 20, and atomic weight 40.08. NCI Thesaurus (NCIt) Calcium appears as a silvery, soft metal that turns grayish white on exposure to air. An isotope is an atom with a different number of neutrons, but the same number of protons and electrons. Each element has a standard number of neutrons that can be found by looking at a periodic table. From the periodic table, you will get the atomic number on the top left corner of the box.
| Isotope | Atomic mass (Da) | Isotopic abundance (amount fraction) |
|---|---|---|
| 40Ca | 39.962 5909(2) | 0.969 41(156) |
| 42Ca | 41.958 618(1) | 0.006 47(23) |
| 43Ca | 42.958 766(2) | 0.001 35(10) |
| 44Ca | 43.955 482(2) | 0.020 86(110) |
| 46Ca | 45.953 69(2) | 0.000 04(3) |
| 48Ca | 47.952 5229(6) | 0.001 87(21) |
In 1983, the Commission with its liberalized policy on uncertainties,was able to recommend as standard atomic weight Ar(Ca) = 40.078(4) weighted toward the mass-spectrometricmeasurements. Moreover, the stated uncertainty includes all chemical,x-ray, and mass-spectrometric measurements believed to be significant by the Commission, as enumerated inits 1983 report.
There is evidence for minor isotope fractionation of calcium in Nature, causing variability ofAr(Ca) in normal sources that is within the uncertainty of the standard atomic weight. Variations inn(44Ca)/n(40Ca) can be reported as δ44Ca values relative to the calcium carbonate reference materialNIST-SRM 915a. A recent compilation yielded a range of published δ44Ca values in naturalsamples from a low of -2.17 ‰ in a cougar bone with Ar(Ca) = 40.0778 to a high of +2.76 ‰ in egg white with Ar(Ca) = 40.0784.Elemental calcium with as δ44Ca = -6.0 ‰ (Ar(Ca) = 40.0773) also has beenreported. Variations in the isotopic composition of marine calcium have occurred over the last 80 Ma.
In addition, there are many reports of anomalous isotopic composition of some minor samples of Ca, some of which may have arisen from the decay of 40K to 40Ca. The annotation 'g' is therefore maintained for this element. 41Ca is an extinct radioisotope (with a half-life of 0.1 Ma), which can be used to date the early history of the solar system through itsdecay to 41K.
© IUPAC 2003
CIAAW
Calcium
Ar(Ca) = 40.078(4) since 1983
The name derives from the Latin calx for 'lime' (CaO) or 'limestone' (CaCO3) in which it was found.It was first isolated by British chemist Humphry Davy in 1808 with help from the Swedish chemist JönsJacob Berzelius and the Swedish court physician M. M. af Pontin.
Atomic Number Of Ca 42
Isotopic reference materials of calcium.