A historian discovers a nineteenth-century notebook in which some observations, dated 1822, were recorded on a substance thought to be a new element. Here are some of the data recorded in the notebook: 'Ductile, silver-white, metallic looking. Softer than lead. Unaffected by water. Stable in air. Melting point: 153 °C. Density: 7.3 gcm3. Electrical conductivity: 20% that of copper. Hardness: About 1% as hard as iron. When 4.20 g of the unknown is heated in an excess of oxygen, 5.08 g of a white solid is formed. The solid could be sublimed by heating to over 800 °C.' (a) Using information in the text and the CRC Handbook of Chemistry and Physics, and making allowances for possible variations in numbers from current values, identify the element reported.

Question

A historian discovers a nineteenth-century notebook in which some observations, dated 1822, were recorded on a substance thought to be a new element. Here are some of the data recorded in the notebook: 'Ductile, silver-white, metallic looking. Softer than lead. Unaffected by water. Stable in air. Melting point: 153 °C. Density: 7.3 g>cm3. Electrical conductivity: 20% that of copper. Hardness: About 1% as hard as iron. When 4.20 g of the unknown is heated in an excess of oxygen, 5.08 g of a white solid is formed. The solid could be sublimed by heating to over 800 °C.' (a) Using information in the text and the CRC Handbook of Chemistry and Physics, and making allowances for possible variations in numbers from current values, identify the element reported.

Accepted Answer

Hey everyone in this example, we need to determine the identity of the unknown solid Melanie Lloyd that is observed to have the following properties. So we're given the property that it's a semi conductor of electricity. We have the following boiling point, which is a very high boiling 0.0.3538 kelvin. We have a very high melting point as well, 1687 kelvin. And then we have a density value of 2.32296 g per millimeter, which is a greater value than the density of water, which we recall. Sorry, there should be a pen Is equal to 1.0 g per mil leader. So it has a greater density of water. So because they tell us in this question that our compound should be a metal Lloyd, we want to recall the metal Lloyd's on our periodic table. So we would consider the metal Lloyd's of our periodic table to be distinguished by either boron, silicon, arsenic, delirium, antimony, germanium. And these are our six metal Lloyd's that we can find on our periodic table. So we want to go ahead and refer to our textbooks as well as our online google searches to find whether these properties correspond to any of the given metal Lloyd's on the right and when we look these properties up, we will see that we have a match to these properties corresponding to our atom silicon here. So when we look up silicon, we would see that it has the boiling point of around this value here, The melting point around this value given, and the density of 2.3296 g per milliliter. And because it's a meta Lloyd, we would recall that metal Lloyd's are semi conductors of electricity. And so because we do have this match of properties with this adam silicon, we would say that this is the identity of the unknown solid metal Lloyd. So this will complete this example as our final answer where S eye represents silicon. So if you have any questions, please leave them down below. Otherwise, I will see everyone in the next practice video.

Verified Solution

Key Concepts

Physical Properties of Metals

Chemical Reactivity and Oxidation

Density and Element Identification