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Chapter 8: Problem 48

Both \(\mathrm{H}^{-}\) and He contain two \(1 s\) electrons. Which species is larger? Explain your choice.

Short Answer

Expert verified
Therefore, He is smaller than \(\mathrm{H}^{-}\) because it has more protons, which results in a greater attractive force pulling the 1s electrons closer to the nucleus.

Step by step solution

01

Understanding The Elements

\(\mathrm{H}^{-}\) represents a hydride ion with an additional electron than a Hydrogen atom. This means it has 1 proton, 1 neutron and 2 electrons. Helium (He) on the other hand, is a noble gas with 2 protons, 2 neutrons and 2 electrons.
02

Size Comparison

The size of an atom or ion is determined by the distance from the nucleus to the outermost shell where there are electrons. In this case, both \(\mathrm{H}^{-}\) and He have their outermost electrons in the same shell (the 1s shell). Therefore we will have to consider the number of protons in the nucleus.
03

The Impact of Nuclear Charge

In a Hydride ion, there is only one proton whereas in a Helium nucleus, there are two. More protons mean more positive charge and thus a greater attractive force for electrons. This greater attraction will 'pull' the electrons closer to the nucleus, thereby decreasing the atomic radius.

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Most popular questions from this chapter

The air in a manned spacecraft or submarine needs to be purified of exhaled carbon dioxide. Write equations for the reactions between carbon dioxide and (a) lithium oxide \(\left(\mathrm{Li}_{2} \mathrm{O}\right),\) (b) sodium peroxide \(\left(\mathrm{Na}_{2} \mathrm{O}_{2}\right),\) and \((\mathrm{c})\) potassium superoxide \(\left(\mathrm{KO}_{2}\right)\)

When magnesium metal is burned in air, it forms two products \(A\) and \(B\). A reacts with water to form a basic solution. B reacts with water to form a similar solution as that of A plus a gas with a pungent odor. Identify A and \(\mathrm{B}\) and write equations for the reactions. (Hint: See Chemistry in Action essay "Discovery of the Noble Gases" in Section \(8.6 .\) )

The first four ionization energies of an element are approximately \(579 \mathrm{~kJ} / \mathrm{mol}, 1980 \mathrm{~kJ} / \mathrm{mol}, 2963 \mathrm{~kJ} /\) mol, and \(6180 \mathrm{~kJ} / \mathrm{mol}\). To which periodic group does this element belong?

Why is the radius of the lithium atom considerably larger than the radius of the hydrogen atom?

Use the alkali metals and alkaline earth metals as examples to show how we can predict the chemical properties of elements simply from their electron configurations.
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