Questions: Which element did Mendeleev predict would have an atomic mass of 68 and be a soft metal? a gallium b erbium c potassium d magnesium

Which element did Mendeleev predict would have an atomic mass of 68 and be a soft metal? a gallium b erbium c potassium d magnesium
Transcript text: Which element did Mendeleev predict would have an atomic mass of 68 and be a soft metal? a gallium b erbium c potassium d magnesium
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Solution

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Solution Steps

Step 1: Understand Mendeleev's Predictions

Mendeleev predicted the existence of elements that were not yet discovered by identifying gaps in his periodic table. He used the properties of surrounding elements to estimate the properties of these missing elements, including atomic mass and physical characteristics.

Step 2: Identify the Predicted Element

Mendeleev predicted an element with an atomic mass of approximately 68 and described it as a soft metal. This prediction was based on the properties of elements surrounding the gap in his periodic table.

Step 3: Match the Prediction to Known Elements

Among the options provided:

  • Gallium (a) is a soft metal with an atomic mass close to 68.
  • Erbium (b) is not a soft metal and has a much higher atomic mass.
  • Potassium (c) is a soft metal but has a lower atomic mass.
  • Magnesium (d) is not a soft metal and has a lower atomic mass.
Step 4: Conclusion

Based on the predicted properties, gallium (a) matches Mendeleev's prediction of an element with an atomic mass of 68 and being a soft metal.

Final Answer

The correct answer is A.

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