Which is larger, the H 1s orbital or the Li 1s orbital? Why? Which has the larger radius, the H atom or the Li atom? Why?

Short Answer

Expert verified
The Li 1s orbital is smaller than the H 1s orbital due to the higher effective nuclear charge experienced by the Li 1s electron (3) compared to the H 1s electron (1). However, the Li atom has a larger atomic radius than the H atom because it has more electron shells.

Step by step solution

01

Understand the concept of effective nuclear charge

Effective nuclear charge (Zeff) is the net charge experienced by an electron in an atom due to the attractive force of the protons and the repulsive force of the other electrons present. It is the difference between the total nuclear charge (Z) and the shielding constant (S). Mathematically, it can be represented as: \(Z_{eff} = Z - S\)
02

Find the effective nuclear charge for the H 1s and Li 1s orbitals

For hydrogen (H), there is only one electron and one proton in the atom. Therefore, there is no shielding effect. The effective nuclear charge experienced by the H 1s electron is equal to the total nuclear charge, which is 1. For lithium (Li), there are three electrons and three protons in the neutral atom. The two 1s electrons shield the outermost 2s electron from the full nuclear charge, but since we are considering the 1s orbital, shielding is negligible because the other 1s electron cannot shield the electron in focus. The effective nuclear charge experienced by the Li 1s electron is approximately equal to the total nuclear charge, which is 3.
03

Compare the size of H 1s and Li 1s orbitals

The size of an atomic orbital is inversely proportional to the effective nuclear charge experienced by the electron occupying that orbital. Since the Li 1s electron experiences a higher effective nuclear charge (3) compared to the H 1s electron (1), the Li 1s orbital is smaller than the H 1s orbital.
04

Find the atomic radii of H and Li atoms

Atomic radii increase down a group and decrease across a period in the periodic table. Hydrogen and lithium are both in Group 1 (alkali metals), but lithium is in Period 2, whereas hydrogen is in Period 1. Lithium has more electron shells, resulting in a larger atomic radius.
05

Summarize the results

In summary, the H 1s orbital is larger than the Li 1s orbital due to the difference in effective nuclear charge. However, the atomic radius of the Li atom is larger than the H atom because it has more electron shells. The bigger orbital size for H 1s does not necessarily mean that the overall size of the hydrogen atom is larger than the lithium atom.

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