how do you know the charge of an element from the periodic table?
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To find the ionic charge of an element you'll need to consult your Periodic Table. On the Periodic Table metals (found on the left of the table) will be positive. Non-metals (found on the right) will be negative.
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Determining Chemical Properties using the Periodic Table. Chemical properties of each element are determined by the element's electronic configuration, and particularly by its outermost valence electrons.
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To calculate the number electrons in the ion. First, add one to the number of protons to find the number of electrons for each negative charge on the ion (-3 ion, add three electrons etc.). For example, NO−3 has: N = 7 protons; 3 O = 3 × 8 = 24 protons; Total = 7 + 24 = 31 protons.
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The atomic numbers are listed along with the names and symbols of the elements on the inside cover of the text. The atomic number equals the charge on the nucleus. It therefore also equals the number of protons in the nucleus and also equals numerically the number of electrons in the neutral atom.
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['Determine the number of electrons that the atom has.', 'Fill the s orbital in the first energy level (the 1s orbital) with the first two electrons.', 'Fill the s orbital in the second energy level (the 2s orbital) with the second two electrons.']
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Electric Charge in the Atom. Atoms contain negatively charged electrons and positively charged protons; the number of each determines the atom's net charge.
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The atomic mass of an element is the total number of protons and neutrons in the nucleus of the atom. The mass number is used to calculate the number of neutrons & electrons in one atom of an element. In order to calculate the number of neutrons you must subtract the atomic number from the atomic mass.
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['Mass → Moles and Moles → Atoms.', '196.967 u . ... ', 'So, if you are given the mass of an element, you use the periodic table to find its molar mass, and multiply the given mass by the reciprocal of the molar mass. ... ', "Once you have moles, multiply by Avogadro's number to calculate the number of atoms."]
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If you have a sample that contains only atoms of a particular element, weigh the sample in grams and divide by the atomic weight of the element. The quotient tells you the number of moles. Multiply that by Avogadro's number, and you'll find out how many atoms the sample contains.
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The key of a periodic table will indicate which number represents the atomic number within each elemental square. The number of protons can be evaluated if the mass number and the number of neutrons of an element are known. The mass number of an element is the number of protons plus the number of neutrons.
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To calculate the molar mass of a molecule, we first obtain the atomic weights from the individual elements in a periodic table. We then count the number of atoms and multiply it by the individual atomic masses. Lastly, we add all the atomic masses together to get the molar mass.
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From the formula and the atomic mass of the atoms you can find the formula weight or molecular mass for the compound. To calculate the formula weight for a compound we will select the atomic mass of each of the elements in the compound from the periodic table, multiply by the number of atoms, and sum the result.
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Subtract the charge from the atomic number if the ion is positive. If the charge is positive, the ion has lost electrons. To determine how many electrons are left, subtract the amount of charge from the atomic number. In this case, there are more protons than electrons.
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Group IV A (14) metals form cations with +4 charge, although tin (Sn) and lead (Pb) can form cations having +2 charge. Generally, metals in this group are treated similarly to the “B” elements. The non-‐metals carbon (C) and silicon (Si) generally don't form cations.
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The charge on the ion tells you the number of electrons. If the charge is positive, subtract that number from the atomic number to get the number of electrons. You have more protons. If the charge is negative, add the amount of charge to the atomic number to get the number of electrons.
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If an ion has a 2+ charge then it must have lost electrons to form the cation. If the ion has 18 electrons and the atom lost 2 to form the ion, then the neutral atom contained 20 electrons. Since it was neutral, it must also have had 20 protons. Therefore the element is calcium.
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['Identify the cation.', 'Write the correct formula and charge for the cation.', 'Identify the anion.', 'Write the correct formula and charge for the anion.', 'Combine the cation and anion to produce an electrically neutral compound.']