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In 2NaCl, there are two atoms of sodium per molecule of NaCl. Therefore, there are 2 atoms of sodium in 2 NaCl molecules.
There are four zinc blende atoms per unit cell.
Halite is sodium chloride, NaCl; NaCl has in the molecule two atoms: 1 Na atom and 1 chlorine atom.
In a face-centered cubic (FCC) structure, which is the crystal structure of silver, there are four atoms per unit cell. This is calculated by considering the contributions from the corner atoms (1/8 of an atom each from 8 corners) and the face-centered atoms (1/2 of an atom each from 6 faces). Therefore, the total is 1 (from corners) + 3 (from faces) = 4 atoms per unit cell.
We just use stoichiometry. The molecular formula for sodium chloride is NaCl. First we must find the molar mass of NaCl, using the molar masses of each element in the compound. So, 23 g/mol of Na + 36 g/mol of Cl = 58 g/mol of NaCl. Next, we take the amount of grams you have (26 grams) and divide it by the molar mass of NaCl to find the number of moles in your sample. 26 g NaCl / 58 g/mol of NaCl = .45 mol NaCl. Finally, we convert that to the number of NaCl molecules in a mole by multiplying .45 moles by 6.02x1023. This equals 2.7x1023 molecules. Because, technically, NaCl is made up of 2 atoms per molecule, you can multiply that by 2, giving 5.7x1023 atoms.
Tungsten has a body-centered cubic (BCC) crystal structure. In a BCC unit cell, there are 2 atoms per unit cell: one atom at the center of the cube and eight corner atoms, each contributing 1/8 of an atom to the unit cell (8 corners x 1/8 = 1). Therefore, the total number of atoms per unit cell for tungsten is 2.
In a diamond unit cell, each carbon atom is located at the corners of the unit cell. Since there are eight corners in a unit cell, each shared by 8 adjacent unit cells, the contribution to the total number of carbon atoms is 1/8 of a carbon atom per unit cell. Therefore, there is 1 carbon atom per unit cell.
To calculate the number of atoms in a unit cell, you first determine the type of unit cell (simple cubic, body-centered cubic, or face-centered cubic) and the number of atoms contributed by each lattice point. Then, you multiply the number of lattice points within the unit cell by the number of atoms contributed per lattice point. For example, a simple cubic unit cell has one atom per lattice point, so the total number of atoms in a simple cubic unit cell would be 1 x 1 = 1 atom.
The formula unit for this compound has a gram molar mass that is the sum of the gram atomic masses for its two constituent atoms, 22.989 + 35.483 = 58.472. Therefore, 2.1 g constitutes 2.1/58.472 = 0.0359 mole. Multiplying this number of moles by Avogadro's number, which is 6.022 X 1023, gives the number of atoms of sodium, 2.2 X 1022 atoms of sodium.
The concentration of NaCl in a solution that contains 0.9 NaCl is 0.9 grams of NaCl per 100 grams of solution.
There are two atoms per unit cell in the Body-Centered Cubic (BCC) crystal structure.
According to the U.S. mint the nickels currently in circulation weigh 5.000 grams and contain 25% Ni (the rest is copper). 25% of 5.000g = 1.250 grams of Ni in a nickel coin / molar mass of Ni 58.71 g/mol = 0.02129 moles of Ni times the number of particles for one mole 6.02x10^23 = 1.28x10^22 atoms of Ni in one coin. All together: (0.25 x 5.000g) / (58.71 g per mol) x (6.02x10^23 atoms per mol) = 1.28x10^22 atoms Ni per coin.