hydrogen-like

Examples of hydrogen-like in the following topics:

• Energy of a Bohr Orbit

  • So, if a nucleus has $Z$ protons ($Z=1$ for hydrogen, $Z=2$ for helium, etc.) and only one electron, that atom is called a hydrogen-like atom.
  • The spectra of hydrogen-like ions are similar to hydrogen, but shifted to higher energy by the greater attractive force between the electron and nucleus.
  • Using this equation, the energy of a photon emitted by a hydrogen atom is given by the difference of two hydrogen energy levels:
  • Bohr's model predicted experimental hydrogen spectrum extremely well.
  • Apply proper equation to calculate energy levels and the energy of an emitted photon for a hydrogen-like atom

• Problems

  • Derive the lifetime of the $n=2, l=1, m=0$ state of hydrogen to emit a photon and end up in the $n=1, l=0, m=0$ state.
  • Consider that the mass fraction of the different atoms are hydrogen (0.7), helium (0.27), carbon (0.008), oxygen (0.016) and iron (0.004).

• Hydrogen Bonding and Van der Waals Forces

  • When polar covalent bonds containing hydrogen form, the hydrogen in that bond has a slightly positive charge because hydrogen’s one electron is pulled more strongly toward the other element and away from the hydrogen.
  • This interaction is called a hydrogen bond.
  • Hydrogen bonds are also responsible for zipping together the DNA double helix.
  • Like hydrogen bonds, van der Waals interactions are weak attractions or interactions between molecules.
  • The slightly negative oxygen side of the water molecule and the slightly positive hydrogen side of the water molecule are attracted to each other and form a hydrogen bond.

• Water’s Polarity

  • The two hydrogen atoms and one oxygen atom within water molecules (H2O) form polar covalent bonds.
  • Water's charges are generated because oxygen is more electronegative, or electron loving, than hydrogen.
  • Thus, it is more likely that a shared electron would be found near the oxygen nucleus than the hydrogen nucleus.
  • Since water is a nonlinear, or bent, molecule, the difference in electronegativities between the oxygen and hydrogen atoms generates the partial negative charge near the oxygen and partial positive charges near both hydrogens.
  • This interactive shows the interaction of the hydrogen bonds among water molecules.

• The Hydrogen Economy

  • The hydrogen economy refers to using hydrogen as the next important source of fuel.
  • Free hydrogen does not occur naturally in quantities of use, like other energy sources, but it can be generated by various methods.
  • Alternatively, liquid hydrogen or slush hydrogen (a combination of liquid and solid hydrogen) can be used.
  • Hydrogen can be stored as a chemical hydride or in some other hydrogen-containing compound.
  • This means that any leak of hydrogen from a hydrogen:air mixture will most likely lead to an explosion if it comes into contact with a spark or flame.

• Water’s States: Gas, Liquid, and Solid

  • The formation of hydrogen bonds is an important quality of liquid water that is crucial to life as we know it.
  • In liquid water, hydrogen bonds are constantly formed and broken as the water molecules slide past each other.
  • On the other hand, when the temperature of water is reduced and water freezes, the water molecules form a crystalline structure maintained by hydrogen bonding (there is not enough energy to break the hydrogen bonds).
  • Cells can only survive freezing if the water in them is temporarily replaced by another liquid like glycerol.
  • Hydrogen bonding makes ice less dense than liquid water.

• Covalent Bonds and Other Bonds and Interactions

  • The electron from the hydrogen splits its time between the incomplete outer shell of the hydrogen atom and the incomplete outer shell of the oxygen atom.
  • When polar covalent bonds containing hydrogen are formed, the hydrogen atom in that bond has a slightly positive charge (δ+) because the shared electrons are pulled more strongly toward the other element and away from the hydrogen atom.
  • The weak interaction between the δ+ charge of a hydrogen atom from one molecule and the δ- charge of a more electronegative atom is called a hydrogen bond.
  • For example, hydrogen bonds are responsible for zipping together the DNA double helix.
  • Like hydrogen bonds, van der Waals interactions are weak interactions between molecules.

• Binary Hydrides

  • A hydride is the anion of hydrogen (H−), and it can form compounds in which one or more hydrogen centers have nucleophilic, reducing, or basic properties.
  • In such hydrides, hydrogen is bonded to a more electropositive element or group.
  • Even certain enzymes, like hydrogenase, operate via hydride intermediates.
  • Instead, many compounds have a hydrogen center with a hydridic character.
  • In these substances, the hydride bond, formally, is a covalent bond much like the bond that is made by a proton in a weak acid.

• Chemiosmosis and Oxidative Phosphorylation

  • During chemiosmosis, electron carriers like NADH and FADH donate electrons to the electron transport chain.
  • This protein acts as a tiny generator turned by the force of the hydrogen ions diffusing through it, down their electrochemical gradient.
  • The overall result of these reactions is the production of ATP from the energy of the electrons removed from hydrogen atoms.
  • The extra electrons on the oxygen attract hydrogen ions (protons) from the surrounding medium and water is formed.
  • In oxidative phosphorylation, the hydrogen ion gradient formed by the electron transport chain is used by ATP synthase to form ATP.

• Hydrogen Bonding

  • A hydrogen bond is a strong intermolecular force created by the relative positivity of hydrogen atoms.
  • A hydrogen atom attached to a relatively electronegative atom is a hydrogen bond donor.
  • This hydrogen atom is a hydrogen bond donor.
  • Greater electronegativity of the hydrogen bond acceptor will create a stronger hydrogen bond.
  • Where do hydrogen bonds form?