Melting point of francium

Take francium s melting point as an example. The plot shows how the melting points of the alkali metals vary with atomic number. From lithium to sodium, the melting point drops 81.4° from sodium to potassium, 34.6° from potassium to rubidium, 24° from rubidium to cesium, 11 °. On the basis of this trend, we can predict that the change from cesium to francium would be about 5°. If so, the melting point of francium would be 23°C, which would make it a liquid under atmospheric conditions. 

A plot of the melting points of the alkali metals versus their atomic numbers. By extrapolation, the melting point of francium should be 23°C. 

Using these melting-point data, estimate the melting point of francium, which is a radioactive element ... 

Other alkali metals The most reactive alkali metals— rubidium, cesium, and francium—have little commercial use. Rubidium, with a melting point of only 40°C, melts on a hot day. It will burst into flames if exposed to air. Francium, the most reactive alkali metal, is a rare radioactive element. For which SI base unit is cesium the atomic standard ... 

Francium-223, with a half-life of 22 minutes, is the longest-lived isotope of the element. Since then it has been found to occur naturally, but there is probably less than an ounce of the element in the Earths crust at any given time. Francium, by extrapolation from the melting points of the other alkali metals, would most Hkely be a liquid if enough of it could be isolated. So far no weighable quantities of the element have been produced. 

Cesium is located between rubidium and francium in group 1 of the periodic table. It is the heaviest of the stable alkali metals and has the lowest melting point. It is also the most reactive of the alkali metals. 

Not a great deal is known about francium s properties, but some measurements of its most stable isotope have been made. Its melting point is 27°C and its boiling point is 677°C, but its density is unknown. It is assumed to have a +1 oxidation state (similar to all the other alkali metals)... 

Look at the properties of the alkali metals summarized in Table 6.4, and predict reasonable values for the melting point, boiling point, density, and atomic radius of francium. 

Using the information on pp. 138-140, predict the properties of the element francium related to its melting point, density and softness. Predict how francium would react with water and write a balanced equation for the reaction. 

Plot the melting points (Table 18.4) of the alkali metals versus atomic number. Predict the melting point for the element francium. Would you predict francium to be a solid or a liquid at room temperature ... 

PRACTICE EXAMPLE A Francium (Z = 87) is an extremely rare radioactive element formed when actinium (Z = 89) undergoes alpha-particle emission. Francium occurs in natural uranium minerals, but estimates are that little more than 15 g of francium exists in the top 1 km of Earth s crust. Few of francium s properties have been measured, but some can be inferred from its position in the periodic table. Estimate the melting point, density, and atomic (metallic) radius of francium. [Hint Plot each property versus atomic number, Z, and extrapolate to Z = 87.]... 

Integrative Example A. Based on rough approximations of the trends of data, the properties of francium can be approximated. Melting point ... 

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