The telluric screw plotted the atomic weights of the elements on the outside of a cylinder, so that one complete turn corresponded to an atomic weight increase of 16. His principal contribution to chemistry was the 'vis tellurique' (telluric screw), a three-dimensional arrangement of the elements constituting an early form of the periodic classification, published in 1862. This area of the website celebrates the work of many famous scientists whose quest to learn more about the world we live in and the atoms that make up the things around us led to the periodic table as we know it today.Ĭan France claim the first periodic table? Probably not, but a French Geology Professor made a significant advance towards it, even though at the time few people were aware of it.Īlexandre Béguyer de Chancourtois was a geologist, but this was at a time when scientists specialised much less than they do today. It was not until a more accurate list of the atomic mass of the elements became available at a conference in Karlsruhe, Germany in 1860 that real progress was made towards the discovery of the modern periodic table. In 1829, Johann Döbereiner recognised triads of elements with chemically similar properties, such as lithium, sodium and potassium, and showed that the properties of the middle element could be predicted from the properties of the other two. Several other attempts were made to group elements together over the coming decades. The earliest attempt to classify the elements was in 1789, when Antoine Lavoisier grouped the elements based on their properties into gases, non-metals, metals and earths. Certainly Mendeleev was the first to publish a version of the table that we would recognise today, but does he deserve all the credit?Ī number of other chemists before Mendeleev were investigating patterns in the properties of the elements that were known at the time. The overall order is Se < Te < Sb, so Se has the most negative electron affinity among the three elements.Ask most chemists who discovered the periodic table and you will almost certainly get the answer Dmitri Mendeleev. Because Sb is located to the left of Te and belongs to group 15, we predict that the electron affinity of Te is more negative than that of Sb. We also know that electron affinities become more negative from left to right across a row, and that the group 15 elements tend to have values that are less negative than expected. Place the elements in order, listing the element with the most negative electron affinity first.Ī We know that electron affinities become less negative going down a column (except for the anomalously low electron affinities of the elements of the second row), so we can predict that the electron affinity of Se is more negative than that of Te. Similarly, use the trends in electron affinities from left to right for elements in the same row. Use the trends in electron affinities going down a column for elements in the same group. Locate the elements in the periodic table.\( \newcommand\): Contrasting Electron Affinities of Sb, Se, and Teīased on their positions in the periodic table, which of Sb, Se, or Te would you predict to have the most negative electron affinity?Īsked for: element with most negative electron affinity
0 Comments
Leave a Reply. |