Position of calcium(Ca) in the periodic table The atomic number is the number of electrons in that element. Therefore, the maximum electron holding capacity in the first shell is two, the second shell is eight and the 3rd shell can have a maximum of eighteen electrons. The maximum electron holding capacity in N orbit is 2n 2 = 2 × 4 2 = 32. The maximum electron holding capacity in M orbit is 2n 2 = 2 × 3 2 = 18. The maximum electron holding capacity in L orbit is 2n 2 = 2 × 2 2 = 8. The maximum electron holding capacity in K orbit is 2n 2 = 2 × 1 2 = 2. The electron holding capacity of each orbit is 2n 2. K is the name of the first orbit, L is the second, M is the third, and N is the name of the fourth orbit. These circular paths are called orbit(shell). The electrons of the atom revolve around the nucleus in a certain circular path. The complete idea of the orbit is given there. Scientist Niels Bohr was the first to give an idea of the atom’s orbit. Calcium atom electron configuration through orbit For example Aufbau principle, Hund’s principle, and Pauli’s exclusion principle. Journal of Agronomic Education 14(2): 84–90.Calcium(Ca) atom electron configuration(Bohr model)Įlectron configuration through orbitals follows different principles. Expressing cation exchange capacity in milliequivalents per 100 grams and in SI units. Soil Fertility and Fertilizers, 8th Edition. publications/ohio-agronomy-guide-15th-edition-bulletin-472 Ohio State University Extension Bulletin 472. While standard soil testing laboratories commonly calculate and report these values in soil test reports, it is helpful to have a solid understanding of CEC and base saturation calculations. Base saturation is closely related to pH as base saturation increases, pH increases.īase Saturation (%) = ( Base cations/CEC) \( x \text \)Ĭation exchange capacity and base saturation are important soil measurements that help determine how a soil is managed and fertilized. Therefore, it has a higher base saturation. Figure 2 shows two soils with the same CEC, but the soil on the right has more base cations (in blue). (Ca 2+ + Mg 2+ + K + + Na +) + (H + + Al 3+ + NH 4 +)įigure 1 illustrates a low CEC soil, with a small number of negative charges and associated cations (left) and a high CEC soil with a larger amount of negative charges, occupied by a greater number of total cations (right).īase saturation is calculated as the percentage of CEC occupied by base cations. Exchangeable cations include base cations, calcium (Ca 2+), magnesium (Mg 2+), potassium (K +) and sodium (Na +), as well as acid cations such as hydrogen (H +), aluminum (Al 3+) and ammonium (NH 4 +). It is measured commonly in commercial soil testing labs by summing cations (positively charged ions that are attracted to the negative surface charges in soil). The relationship between soil texture and CECĬation exchange capacity is defined as a soil’s total quantity of negative surface charges. Values over 25 meq/100 g soil are found with heavy clay soils, organic, or muck soils. Soils in Ohio can encompass a wide CEC range, but typically fall somewhere between 5 to 25 meq/100 g soil (Table 1).
Soil CEC typically increases as clay content and organic matter increase because cation exchange occurs on surfaces of clay minerals, organic matter, and roots. It is the potential of available nutrient supply, not a direct measurement of available nutrients. Cation Exchange Capacity (CEC)Ĭation exchange capacity (CEC) is a fundamental soil property used to predict plant nutrient availability and retention in the soil. The purpose of this fact sheet is to define soil cation exchange capacity, base saturation and calcium saturation, and demonstrate how these values are calculated in soil test reports.
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