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![promethium(III) fluoride | elemental composition](../image_source/c4f0a7b61439de71c37155828bdce9bd.png)
promethium(III) fluoride | elemental composition
Result
![Find the elemental composition for promethium(III) fluoride in terms of the atom and mass percents: atom percent = N_i/N_atoms × 100% mass percent = (N_im_i)/m × 100% Plan: • Write the chemical formula and gather atomic masses from the periodic table. • Determine values for N_i, m_i, N_atoms and m using these items. • Finally, compute the percents and check the results. Write the chemical formula: PmF_3 Use the chemical formula to count the number of atoms, N_i, for each element and find the total number of atoms, N_atoms, per molecule: | number of atoms F (fluorine) | 3 Pm (promethium) | 1 N_atoms = 3 + 1 = 4 Divide each N_i by N_atoms to calculate atom fractions. Then use the property that atom fractions must sum to one to check the work: | number of atoms | atom fraction F (fluorine) | 3 | 3/4 Pm (promethium) | 1 | 1/4 Check: 3/4 + 1/4 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent F (fluorine) | 3 | 3/4 × 100% = 75.0% Pm (promethium) | 1 | 1/4 × 100% = 25.0% Look up the atomic mass, m_i, in unified atomic mass units, u, for each element in the periodic table: | number of atoms | atom percent | atomic mass/u F (fluorine) | 3 | 75.0% | 18.998403163 Pm (promethium) | 1 | 25.0% | 145 Multiply N_i by m_i to compute the mass for each element. Then sum those values to compute the molecular mass, m: | number of atoms | atom percent | atomic mass/u | mass/u F (fluorine) | 3 | 75.0% | 18.998403163 | 3 × 18.998403163 = 56.995209489 Pm (promethium) | 1 | 25.0% | 145 | 1 × 145 = 145 m = 56.995209489 u + 145 u = 201.995209489 u Divide the mass for each element by m to calculate mass fractions. Then use the property that mass fractions must sum to one to check the work: | number of atoms | atom percent | mass fraction F (fluorine) | 3 | 75.0% | 56.995209489/201.995209489 Pm (promethium) | 1 | 25.0% | 145/201.995209489 Check: 56.995209489/201.995209489 + 145/201.995209489 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent F (fluorine) | 3 | 75.0% | 56.995209489/201.995209489 × 100% = 28.2% Pm (promethium) | 1 | 25.0% | 145/201.995209489 × 100% = 71.8%](../image_source/697fc896fa8813625d0cf65dc34aab82.png)
Find the elemental composition for promethium(III) fluoride in terms of the atom and mass percents: atom percent = N_i/N_atoms × 100% mass percent = (N_im_i)/m × 100% Plan: • Write the chemical formula and gather atomic masses from the periodic table. • Determine values for N_i, m_i, N_atoms and m using these items. • Finally, compute the percents and check the results. Write the chemical formula: PmF_3 Use the chemical formula to count the number of atoms, N_i, for each element and find the total number of atoms, N_atoms, per molecule: | number of atoms F (fluorine) | 3 Pm (promethium) | 1 N_atoms = 3 + 1 = 4 Divide each N_i by N_atoms to calculate atom fractions. Then use the property that atom fractions must sum to one to check the work: | number of atoms | atom fraction F (fluorine) | 3 | 3/4 Pm (promethium) | 1 | 1/4 Check: 3/4 + 1/4 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent F (fluorine) | 3 | 3/4 × 100% = 75.0% Pm (promethium) | 1 | 1/4 × 100% = 25.0% Look up the atomic mass, m_i, in unified atomic mass units, u, for each element in the periodic table: | number of atoms | atom percent | atomic mass/u F (fluorine) | 3 | 75.0% | 18.998403163 Pm (promethium) | 1 | 25.0% | 145 Multiply N_i by m_i to compute the mass for each element. Then sum those values to compute the molecular mass, m: | number of atoms | atom percent | atomic mass/u | mass/u F (fluorine) | 3 | 75.0% | 18.998403163 | 3 × 18.998403163 = 56.995209489 Pm (promethium) | 1 | 25.0% | 145 | 1 × 145 = 145 m = 56.995209489 u + 145 u = 201.995209489 u Divide the mass for each element by m to calculate mass fractions. Then use the property that mass fractions must sum to one to check the work: | number of atoms | atom percent | mass fraction F (fluorine) | 3 | 75.0% | 56.995209489/201.995209489 Pm (promethium) | 1 | 25.0% | 145/201.995209489 Check: 56.995209489/201.995209489 + 145/201.995209489 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent F (fluorine) | 3 | 75.0% | 56.995209489/201.995209489 × 100% = 28.2% Pm (promethium) | 1 | 25.0% | 145/201.995209489 × 100% = 71.8%
Mass fraction pie chart
![Mass fraction pie chart](../image_source/23e7d3ca12fee80720b643b0f99bb7ff.png)
Mass fraction pie chart