What is Calcium: Definition and 80 Discussions

Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust, and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The name derives from Latin calx "lime", which was obtained from heating limestone.
Some calcium compounds were known to the ancients, though their chemistry was unknown until the seventeenth century. Pure calcium was isolated in 1808 via electrolysis of its oxide by Humphry Davy, who named the element. Calcium compounds are widely used in many industries: in foods and pharmaceuticals for calcium supplementation, in the paper industry as bleaches, as components in cement and electrical insulators, and in the manufacture of soaps. On the other hand, the metal in pure form has few applications due to its high reactivity; still, in small quantities it is often used as an alloying component in steelmaking, and sometimes, as a calcium–lead alloy, in making automotive batteries.
Calcium is the most abundant metal and the fifth-most abundant element in the human body. As electrolytes, calcium ions play a vital role in the physiological and biochemical processes of organisms and cells: in signal transduction pathways where they act as a second messenger; in neurotransmitter release from neurons; in contraction of all muscle cell types; as cofactors in many enzymes; and in fertilization. Calcium ions outside cells are important for maintaining the potential difference across excitable cell membranes, protein synthesis, and bone formation.

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  1. jedishrfu

    Medical A First of Its Kind: A Calcium-based signal in the Human Brain

  2. C

    Chemistry Understanding electronic configuration

    I don't really understand this electronic configuration of a thing. Suppose I want show the electronic configuration of calcium, how do I show it? Is like this 2, 8, 8, 2 or $$1s^22s^22p^63s^23p^64s^2$$
  3. P

    Help with Atomic Calcium Electron Configurations

    Hi everyone! I need some help in a specific task. It´s about this problem: An excited state of atomic calcium has the electron configuration 1s 2 2s 2 2p6 3s 2 3p6 3d1 4f 1 . (a) Derive all the term symbols (with the appropriate specifications of S, L, and J) for the electron configuration. (b)...
  4. O

    Off by order of magnitude when calculating how much calcium is in bone

    I think I have the answer, but when I calculate it out, I'm off by at least an order of magnitude. My process goes like this: The (looked up) specific activity of Ca-49 is ##1.63*10^7 TBq/g##, which is ##1.63*10^{16} KBq/g## The activity of the sample after 5 minutes rest is ##166KBq##, per...
  5. Fishworks

    Calcium in Anhydrous Calcium Chloride

    Hi All, Does anyone know the Calcium Content Percentage% in Calcium Chloride Anhydrous? I have tried google searching with no results. Thanks :)
  6. P

    Question about Calcium Nitride

    I know calcium nitride is Ca3N2, but why doesn't CaN2 exist (or at least not that I can find)?
  7. G

    Sodium or calcium hypochlorite related to 2.5% active chlorine?

    is sodium or calcium hypochlorite related to 2.5% active chlorine? in a cleaning product it has the following composition: sodium or calcium hypochlorite, active chlorine
  8. DaveC426913

    What caused this calcium deposit?

    A have a deposit of calcium on the glass heater in my (freshwater) aquarium that does not seem to look or act like deposits I am used to. To address some of the obvious questions: A sample of it got nice and fizzy in a puddle of vinegar, so I have little doubt it is calcium. I know calcium...
  9. J

    I Solar chromosphere: inter-conversion of Ca I, Ca II, role of photons

    My question relates to the physics of the emission line of Ca II which originates in the solar chromosphere. My understanding is that ionized Ca which lacks a single electron in its valence orbital interacts with free electron in the chromosphere milieu to form Ca I (nonionized). The captured...
  10. L

    Calcium: Dissolved vs. Undissolved in the Body & Environment

    Regarding calcium in the bloodstream, in drinking water, and in food. Are calcium ions always single, free atoms? Is that the definition of "dissolved?" (single atoms?) Does the bloodstream contain any undissovled calcium? how much? how big? Does drinking water contain any...
  11. Shea Thompson

    Help converting the NIST spectrogram of Calcium

    I am not a physics major and don't know even where to start trying to interpet this spectrogram from the NIST website of the element Calcium https://physics.nist.gov/PhysRefData/Handbook/Tables/calciumtable2.htm My goal is to find a way of converting this spectrogram into a tone or frequency...
  12. KtinaN904

    What is the best way to digest Aluminum from Calcium oxide

    Homework Statement I am attempting to find Alppm from a calcium oxide sample by spectrophotometry. Homework EquationsThe Attempt at a Solution I’ve used conc. HCl and heated to dryness, then added 50/50 HCl and reheated. I then filtered the solution and corrected the pH. I’ve followed the...
  13. C

    Solubility of Calcium Oxalate in an Alcohol Solution?

    In searching through the literature for the solubility of calcium oxalate, I came across this post https://www.researchgate.net/post/Are_there_any_organic_inorganic_solvents_for_dissolving_Ca-oxalate I am not sure where the people answering this question have gotten the information that calcium...
  14. M

    Is Calcium Citrate Effective for Treating Acidosis?

    I read that calcium citrate can be used to treat acidosis, thus when the blood pH shifts just a bit too much to the left. a) calcium citrate is the salt of citric acid. It doesn't seem to work as an antacid. Why does it work to raise pH in the blood then if it's not a base as such? b) is...
  15. B

    Preparation of murexide indicator for Ca measurement

    I want to prepare murexide indicator for Ca measurement using EDTA titrimetric method. I am following the procedure set by the American Public Health Association (APHA), however, I only have murexide diluted with K2SO4 (1:250). I want to know if I can use this as a substitute, and if yes, how...
  16. Z

    Calculating the Ksp of Calcium hydroxide at room temp

    Homework Statement I conducted a titration experiment in which 0.1g of KHP was dissolved in 50mL of distilled water and placed in an Erlenmeyer flask. I filtered a Ca(OH)2 solution (that was left out open on the lab benches for us to use) and put that into the burette and titrated. Ultimately...
  17. C

    Equilibrium pressure of calcium carbonate

    Homework Statement Calcium carbonate primarily occurs as two crystalline forms, calcite and aragonite. The value of∆!° for the transition CaCO3(calcite) ⇌ CaCO3(aragonite) is +1.04 kJ·mol-1 at 25°C. At that temperature the density for calcite is 2.710 g·cm-3, and that of aragonite is 2.930...
  18. J

    Terms Allowed in Spectroscopic Structure of Calcium

    Homework Statement Why can't we have 4s^2 3S1 calcium? I've looked up a table of terms and this is never given, so I guess we can't have it. Why can't the spins of each of the outer electrons add to give S = 1, J = 1, and a degeneracy of 3? I guess the answer must be pretty basic since nobody...
  19. N

    How many atoms of oxygen are present in 300 grams of calcium

    Homework Statement How many atoms of oxygen are present in 300 grams of calcium carbonate? molar mass of CaCO3 = 100g Homework Equations The Attempt at a Solution I don't know how to proceed. Can anyone please help me out by giving the forulae or steps on how to do this problem.
  20. nisler.1

    Trying to run QM/MM simulation with calcium binding protein

    Hello everyone, I'm a graduate student in a biophysics lab. I'm trying to run a QM/MM simulation with a protein that binds 3 Ca2+ ions, and as such I am having a devil of a time getting the SCF to converge. I've tried DIIS, KDIIS, damping, and a few other methods to try to get convergence with...
  21. sciencejournalist00

    Can calcium ions be used as a source of entangled photons

    By heating calcium in a tantalum oven and subjecting the calcium vapor stream to blue laser, calcium atoms absorb the blue photons and emit two photons of lower energy as they decay twice. Once they decay from the highest excited state to an intermediate excited state, and then from the...
  22. L

    Maximum ratio of calcium, atp hydrolysis

    Hello, 1-The standard free energy associated to the hydrolysis of one ATP mole is -31 kJ. What would be the energy when [ATP]=5mM , [ADP]=0.5mM and [Pi]=1mM 2-Calculate the free energy required to move 1 mol of Ca2+ ions from the outside of the cell (where [Ca2+] = 10-3) to the inside (where...
  23. moenste

    Ratio of potassium atoms to calcium atoms in 1 hour

    Homework Statement Potassium 44 (4419K) has a half-life of 20 minutes and decays to form 1420Ca, a stable isotope of calcium. (a) How many atoms would there be in a 10 mg sample of potassium 44? (b) What would be the activity of the same? (c) What would the activity be after one hour? (d) What...
  24. Eclair_de_XII

    How do I calculate the density of calcium from atomic radius?

    Homework Statement "Calcium crystallizes in a body-centered cubic structure. (a) How many Ca atoms are contained in each unit cell? (b) How many nearest neighbors does each Ca atom possess? (c) Estimate the length of the unit cell edge, a, from the atomic radius of calcium (1.97A). (d) Estimate...
  25. Dong Aleta

    A question about the special case of calcium hydroxide

    Hi! I am having trouble understanding how a substance only slightly soluble in water is considered as a strong base. Isn't the definition of a base a substance that will increase the amount of OH- in a solution? In that case, shouldn't calcium hydroxide be considered a weak base because of its...
  26. Dannalee Jayvia

    Water Hardness. Calculating Calcium.

    Homework Statement I have been asked to determine the concentration of calcium ions, in a 100 mL sample of water. Eriochrome black T Indicator was used. Magnesium was removed through a precipitate. The water sample changes colour to red. pH 10 buffer solution was also used. the 3 test amounts...
  27. M

    Unwanted Calcium Carbonate in Refractory Cement

    I have noticed that most castable refractories effervesce if mixed with acid. In context, this is orthophosphoric acid added to promote the formation of a calcium-aluminium phosphate bonding phase. In one case, I estimated that 40% of the calcium aluminate cement had become carbonated by...
  28. E

    Will Ca(HCO3)2(aq) + 2NH3(aq) react?

    Hi, I'm wondering if an aqueous solution of Calcium Bicarbonate and Ammonia would react to form Ammonium Bicarbonate and Calcium Hydroxide. Additionally, would Calcium Carbonate react with Ammonia in solution to form Ammonium Carbonate? EJ
  29. U

    What Transitions Create Calcium's Emission Lines at These Wavelengths?

    Homework Statement Strong emission lines from calcium were observed at ##422.7nm##, ##610.3nm##, ##612.3nm##, ##616.3nm##, ##1034.9nm##, from transitions between ##4s^2##, ##4s5s## and ##4s4p##. The transition of ##422.7nm## was also observed at absorption. The singlet-triplet splitting of...
  30. G

    Is there any reaction happens when calcium ion added to calcium hydroxide?

    Silly question lol But Is there any reaction if calcium ion added to calcium hydroxide? If NaOH or any alkali is added to metal ions, insoluble metal hydroxide is formed. So, what if weak alkali Calcium hydroxide is added to Calcium ion, what will it happen? Will it has no reaction just like...
  31. A

    Hydrogel limiting diffusion of calcium

    Dear scientists, For my thesis I am searching for a hydrogel that limits the diffusion of calciumions. The objective of this is to get the calciumconcentration in the hydrogel within a certain measurable (with fluorescent Cameleon) range. Unfortunately I don't know where to start looking, do...
  32. Y

    Calcium Carbonate & Dicalcium Phosphate - CO2 Problem

    Hello everyone, I would really appreciate your help on figuring out the issue of undesirable CO2 production in this situation. Homework Statement In a mixture of CaCO3 + CaHPO4; I am observing undesirable CO2 production under conditions of 20-25°C (room temp) and an undesirable excess of...
  33. W

    Thermal decomposition of calcium carbonate - problem

    Hello, here goes the problem: The mass of calcium carbonate upon thermal decomposition decreased by 1/5. (a) How many molecules of CaCO3 per 100 molecules were decomposed to CaO and CO2. (b) The content of CaO in the final sample express in molar fraction. My solution: I set the starting...
  34. M

    Thermal decomposition of calcium carbonate ?

    In general, we heat CaCO3 to temperature of approximately 825°C it decomposes into calcium oxide and liberates carbon dioxide gas: CaCO3 →825°C→ CaO + CO2 Is it possible to heat the calcium carbonate at temperatures below 825 degrees Celsius, so the decomposition into calcium oxide.
  35. D

    Slow precipitation of calcium carbonate.

    Hello Everyone, I am working with CaCO3. I want to have the precipitated CaCO3 in the laboratory. The easy way is to mix Na2CO3 and CaCl2. It gives CaCO3 and NaCl but this reaction takes place in a flash. As the reaction rate is high the produced CaCO3 forms powder like substance (the syze of...
  36. G

    Calcium Bromide (Anhydrous) Not Dissolving?

    Hi All, So, I am having trouble with a solution I am trying to prepare in the lab which baffles me and here it is: --Water used is DI Millipore Grade Water-- I have Calcium Bromide (Anhydrous) %99.5 from Alfa-Aesar, CaBr(2) is supposed to be highly soluble about 125g/100ml at 0 Degrees...
  37. V

    Calcium Carbonate -> Calcium Oxide, but only getting Hydroxide. Ideas?

    I was trying to calcine some CaCO3 (Calcium Carbonate), but ended up with Calcium Hydroxide. To test if I had Calcium Carbonate I added it to some vinegar, no gas was produced. I then mixed in a small amount of the powder with a large amount of water and passed CO2 through it, and it became a...
  38. T

    Transition of Calcium Hydrogen-like Ion

    Homework Statement A hydrogen‑like ion of calcium emits a photon with energy E = 756 eV. What transition was involved? Homework Equations The energy equation: E=Z^2*E_R*(1/n^2-1/n'^2) The Attempt at a Solution First, Z=20 for a calcium ion, and E_R is the Rydberg energy 13.6 eV...
  39. A

    Questions about calcium hydroxide as co2 absorber.

    I want to improve our company's packaging strategy for live seafood products. The catch is, the box has to be sealed completely. This causes problem with the ever increasing level of CO2 and not enough o2. Now, since the box is tightly packed with the products and other materials for cushion...
  40. Z

    Where can I find a molecule layout for calcium perchlorate tetrahydrate on Mars?

    The rover on Mars reported on Mars dirt samples, and they talked about calcium perchlorate tetrahydrate. I have been searching for a molecule layout of this chemical (like a pdb or cis style file) that can be viewed in say JMOL with no luck. Does anyone know a good site to get layouts of...
  41. J

    HELP - voltage gated calcium channels

    Referring to following video, I would like to know more about voltage gated calcium channels, will this process called action potential? How do Calcium ion recycle during this process? I can find a lot of materials on action potential for Na+/K+ pump along axon, but not much materials talking...
  42. P

    Calcium carbonate sample -> calcite or aragonite?

    Calcium carbonate sample --> calcite or aragonite? Is there a definite way to determine whether a calcium carbonate sample is calcite or aragonite? The weak bond of aragonite should produce an active reaction with a weak acid such as diluted acetic (vinegar), whereas calcite will require a...
  43. S

    How Does Pressure Influence the Stability of Calcium Carbonate Phases?

    Homework Statement Calcium carbonate (\mathrm{CaCO_3}) has two common crystal forms: Calcite and Aragonite. In room temperature and atmospheric pressure, the Calcite has Gibbs energy -1128.8 kJ/mol, volume 36.93 cm^3/mol and entropy 92.9 J/K/mol, and the Aragonite has Gibbs energy -1127.8...
  44. G

    Calcium current to amount of substance units (mol)

    Hi there... I have a differential equation with to terms: \frac{d[Ca2+]}{dt}=f\Big(\frac{3I_{Ca}}{z 4 \pi r^3 F}-k_{Ca}[Ca2+]\Big) I think that the first term converts the Ca2+ (density of?) current to mol units. But, where does it comes from? z is the valence; in this case of the...
  45. F

    Removing Water from Calcium Silicate (CaSi2H5.nH2O)

    I want to use calcium silicate (CaSiO3) as my reactant, but the suplier give me CaSi2H5.nH2O. He says that this one is calcium silicate. I just wonder to know how to remove the water (nH2O) so i get the CaSiO3?
  46. S

    Action potential of a skeletal muscle fibre,where is calcium?

    Now I follow this pic, there is no mention of opening of calcium channels anywhere. So how do skeletal muscles contract, without calcium. Incontrast action potential of a cardiac muscle has plateu phase and calcium channel involvement. Thanks :smile:
  47. L

    Electron densities of Carbon Strontium water calcium

    Hi, can anyone tell me what the electron densities of Carbon Strontium water calcium are? i can't find it anywhere on the web. Thanks
  48. M

    Reactions of calcium carbonate

    Hi What is the reaction of calcium carbonate and water. I thought it was insoluble but I was looking up some notes from a chemistry practical i did and it says CaCO3(s) + H2O (l) → Ca(OH)2(s) + CO2(g) Can someone please explain this reaction for me as I can't find it on the internet...
  49. C

    In the synthesis of ester, how does conc. aqueos calcium chloride

    In the synthesis of ester, how does conc. aqueos calcium chloride remove excess ethanol? I tried google, and found out that a complex is formed. How is this possible? If then what exactly is the complex formed? Thanks. :smile:
  50. M

    Two concentrations of calcium ions inside and outside the membrane

    This isn't homework - just working through questions in my text. The question gives two concentrations of calcium ions inside and outside the membrane and asks to find the Nernst potential - ok no problem there. Then it asks if the calcium ions are in equilibrium if the resting potential is...