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Chapter 7: Problem 74

Little is known about the properties of astatine, At, because of its rarity and high radioactivity. Nevertheless, it is possible for us to make many predictions about its properties. (a) Do you expect the element to be a gas, liquid, or solid at room temperature? Explain. (b) Would you expect At to be a metal, nonmetal, or metalloid? Explain. (c) What is the chemical formula of the compound it forms with Na?

Short Answer

Expert verified
Astatine is likely a solid at room temperature due to its position in the halogen group and the trends in melting and boiling points among elements in group 17. It is a nonmetal, as its position and group association in the periodic table indicate nonmetallic character. The chemical formula of the compound formed with sodium (Na) is NaAt, with sodium forming a +1 ion and astatine forming a -1 ion.

Step by step solution

01

(a) Determining the state of astatine at room temperature.

To predict whether astatine is a gas, liquid, or solid at room temperature, we should look at its position in the periodic table. Astatine is in group 17, also known as the halogen group. The elements above astatine in this group, such as fluorine and chlorine, are gases at room temperature, while those below it, like iodine and bromine, are solids and liquids respectively. Based on these trends, astatine is likely a solid at room temperature. This is because as we move down the group, the atomic radius increases, which results in stronger van der Waals forces between the atoms, making it higher to higher melting and boiling points.
02

(b) Identifying astatine as a metal, nonmetal, or metalloid.

To determine if astatine is a metal, nonmetal, or metalloid, we can examine its position in the periodic table. Astatine is in the halogen group (group 17), which is composed of nonmetals. As we move from left to right across a period in the periodic table, metallic character decreases, and nonmetallic character increases. Since astatine is on the right side of the periodic table and is a member of the halogen group, we can predict that it is a nonmetal.
03

(c) Predicting the chemical formula of the compound formed with sodium.

To predict the chemical formula of the compound formed between astatine and sodium (Na), we need to consider the common oxidation states of these elements. Sodium, an alkali metal in group 1 of the periodic table, typically forms a +1 ion (losing one electron). Astatine, being in group 17 (the halogen group), typically forms a -1 ion (gaining one electron) since it is a nonmetal. Based on this, the compound formed between sodium and astatine would have the chemical formula NaAt, as the +1 charge of the sodium and the -1 charge of the astatine will balance each other out.

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Most popular questions from this chapter

Arrange the following oxides in order of increasing acidity: $\mathrm{K}_{2} \mathrm{O}, \mathrm{BaO}, \mathrm{ZnO}, \mathrm{H}_{2} \mathrm{O}, \mathrm{CO}_{2}, \mathrm{SO}_{2}$

Based on their positions in the periodic table, predict which atom of the following pairs will have the smaller first ionization energy: (a) $\mathrm{Br}, \mathrm{Kr} ; \mathbf{( b )} \mathrm{C}, \mathrm{Ca} ;(\mathbf{c}) \mathrm{Li}, \mathrm{Rb} ;\(; (d) \)\mathrm{Pb}, \mathrm{Si} ;$ (e) \(\mathrm{Al}, \mathrm{B}\).

Write a balanced equation for the reaction that occurs in each of the following cases: (a) Potassium metal is exposed to an atmosphere of chlorine gas. (b) Strontium oxide is added to water. (c) A fresh surface of lithium metal is exposed to oxygen gas. (d) Sodium metal reacts with molten sulfur.

(a) Use orbital diagrams to illustrate what happens when an oxygen atom gains two electrons. (b) Why does \(\mathrm{O}^{3-}\) not exist?

Detailed calculations show that the value of \(Z_{\text {eff }}\) for the outermost electrons in \(\mathrm{Si}\) and \(\mathrm{Cl}\) atoms is \(4.29+\) and \(6.12+,\) respectively. (a) What value do you estimate for \(Z_{\text {eff }}\) experienced by the outermost electron in both Si and Cl by assuming core electrons contribute 1.00 and valence electrons contribute 0.00 to the screening constant? (b) What values do you estimate for \(Z_{\text {eff }}\) using Slater's rules? (c) Which approach gives a more accurate estimate of \(Z_{\text {eff }} ?\) (d) Which method of approximation more accurately accounts for the steady increase in \(Z_{\text {eff }}\) that occurs upon moving left to right across a period? (e) Predict \(Z_{\text {eff }}\) for a valence electron in P, phosphorus, based on the calculations for \(\mathrm{Si}\) and \(\mathrm{Cl}\).
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