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In a simple model of a hydrogen atom, the single electron orbits the single proton (the nucleus) in a circular path. Calculate (a) the electric potential set up by the proton at the orbital radius of \(52.9 \mathrm{pm},\) (b) the electric potential energy of the atom, and (c) the kinetic energy of the electron. (d) How much energy is required to ionize the atom (that is, to remove the electron to an infinite distance with no kinetic energy)? Give the energies in electron-volts.

Short Answer

Expert verified
Ionization energy is 27.2 eV, with potentials 27.2 V, potential energy 27.2 eV, and kinetic energy 13.6 eV.

Step by step solution

01

Calculate the Electric Potential

The electric potential, \( V \), at a distance \( r \) from a point charge \( q \) is given by \( V = \frac{kq}{r} \), where \( k \) is Coulomb's constant \( 8.99 \times 10^9 \, \text{N m}^2 / \text{C}^2 \) and \( q \) is the charge of the proton \( 1.60 \times 10^{-19} \, \text{C} \). With an orbital radius of \( 52.9 \, \text{pm} = 52.9 \times 10^{-12} \, \text{m} \), the potential is calculated as: \[ V = \frac{8.99 \times 10^9 \, \text{N m}^2 / \text{C}^2 \times 1.60 \times 10^{-19} \, \text{C}}{52.9 \times 10^{-12} \, \text{m}} = 27.2 \, \text{V}. \]
02

Calculate the Electric Potential Energy

The electric potential energy, \( U \), of the electron is given by \( U = qV \), where \( V \) is the potential calculated in Step 1. So, \( U = (1.60 \times 10^{-19} \, \text{C})(27.2 \, \text{V}) = 4.35 \times 10^{-18} \, \text{J} \). To convert to electron-volts (1 eV = \( 1.60 \times 10^{-19} \, \text{J} \)), divide by \( 1.60 \times 10^{-19} \), giving \( 27.2 \, \text{eV} \).
03

Calculate the Kinetic Energy of the Electron

In this model, the kinetic energy (KE) equals the absolute value of the potential energy divided by two: \( KE = \frac{|U|}{2} \). Using \( U = 27.2 \, \text{eV} \), the kinetic energy is: \[ KE = \frac{27.2}{2} = 13.6 \, \text{eV}. \]
04

Calculate the Ionization Energy

The energy required to ionize the atom is the sum of the kinetic energy and the potential energy (absolute value) because it means bringing the electron to an infinite distance: \( E_{\text{ionization}} = KE + |U| = 13.6 \, \text{eV} + 13.6 \, \text{eV} = 27.2 \, \text{eV}. \)

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Electric Potential
The concept of electric potential is foundational in understanding how charged particles interact. In this exercise, the proton in a hydrogen atom creates an electric potential field around itself. This potential is defined as the amount of work needed to bring a unit positive charge from far away to a point in the field without acceleration.
To calculate the electric potential at a point, use the formula:
  • \( V = \frac{kq}{r} \)
Here, \( k \) is Coulomb's constant, \( q \) is the charge of the proton, and \( r \) is the distance from the charge.
In the Bohr model example, the electron orbiting the nucleus experiences a potential of 27.2 volts at its orbital radius. This value represents the energy per charge that the proton imparts at this radius, showing how closely electric potential is tied to particle interactions in the atom.
Electric Potential Energy
Electric potential energy is a measure of the work required to position an electric charge within an electric field. For an electron in a hydrogen atom, its potential energy depends on its charge and the electric potential at its location.
The equation to find potential energy \( U \) from potential \( V \) is:
  • \( U = qV \)
For the hydrogen atom, with \( q = 1.60 \times 10^{-19} \, \text{C} \) and \( V = 27.2 \, \text{V} \), the potential energy is calculated as 4.35 x 10^-18 Joules. Converting this to electron-volts, which is a more suitable energy unit for atomic scale calculations, gives us 27.2 eV.
This potential energy represents the stored energy due to the electron’s position within the proton's field, illustrating the attraction that keeps the electron in orbit.
Kinetic Energy
Kinetic energy (KE) describes the energy of motion and is a crucial part of understanding an electron's behavior within an atom. According to the Bohr model, an electron's kinetic energy is related to its potential energy.
Specifically, the kinetic energy is half the magnitude of the electric potential energy:
  • \( KE = \frac{|U|}{2} \)
In the case of our hydrogen atom, with potential energy at 27.2 eV, the electron’s kinetic energy becomes 13.6 eV. This accounts for the energy due to the electron’s orbital motion around the nucleus. Understanding kinetic energy is key in providing insight into the electron’s movement and stability within the atom.
Ionization Energy
Ionization energy is the energy required to remove an electron from an atom, overcoming the attraction of the nucleus. This concept is crucial in atomic physics as it determines an atom’s tendency to form ions.To calculated it, both the kinetic and potential energies must be considered.
  • \( E_{\text{ionization}} = KE + |U| \)
In our hydrogen atom model, since both kinetic and potential energies are 13.6 eV, the total ionization energy needed is 27.2 eV. This value indicates the energy necessary to remove the electron to a position where it is unaffected by the proton’s electric field, essentially at an infinite distance. This understanding is fundamental for applications that involve electromagnetic interactions or bonding.

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