Electric charge and energy in an atom

About electric charge and energy in an atom
  • An atom has a set number of particles that determines what kind of element they are.
  • Each element has a specific number of protons (positive charge) in its nucleus. It is this number that defines an element and cannot change in everyday situations.
  • Protons in the nucleus of an atom are very stable and don’t typically move around or get created or destroyed. There are a fixed number and they maintain their positive charge within the atom.
  • Electrons (negative charge) surround the nucleus, with the number typically matching the number of protons to create a neutral atom.
  • Regardless of their energy level, an atom retains the same number of electrons it started with.
  • If an atom loses or gains an electron, it is no longer considered the same element and becomes an ion.
  • The movement of electrons within an atom doesn’t change their total charge because the number of protons and electrons remains constant. However, the movement of electrons does affect the amount of energy within the atom.
  • Electrons in an atom change energy levels as they gain and lose energy.
  • So when an electron absorbs energy (such as visible light), it jumps to a higher energy level further away from the nucleus. However, the electron itself remains negatively charged, it just occupies a different position within the atom.

Heating atoms to produce light

About heating atoms to produce light

When heat excites atoms, the electrons around the nucleus change their energy levels and behaviour. Here is an outline of the process:

Energy Levels and Excitation
  • Atoms have distinct energy levels in the areas around the nucleus where electrons reside. The lowest energy level, called the ground state, provides the bottom step. Excitation occurs when atoms absorb energy, such as heat, causing their electrons to jump to higher energy levels (like climbing the ladder).
  • Heat energy comes in the form of electromagnetic radiation, such as light or infrared waves. When electromagnetic radiation (photons) collide with atoms, they can transfer their energy to the electrons. If the transferred energy matches the difference between two energy levels in the atom, the electron absorbs it and “excites” to the higher level.
  • When infrared waves are absorbed by matter, they cause the molecules in that matter to vibrate more intensely. This increased vibration translates to increased temperature, heating the material. This is how things like infrared heaters, remote controls, and even the warmth you feel from sunlight (excluding the visible light portion) work.
Light Emission

In many cases, the excited atom releases the energy as another photon (light particle) with a specific wavelength corresponding to the energy difference between the initial and final levels. This is how processes like incandescent light, neon signs, and some types of lasers work.

  • When an object (or atom) releases energy, it can sometimes release that energy in the form of infrared waves. This happens because excited atoms or molecules can transition to lower energy levels by emitting infrared photons (particles of light). This type of release is common in many natural and man-made processes, such as:
    • Objects radiating heat: All objects with a temperature above absolute zero radiate some infrared waves because of their internal thermal energy.
    • Chemical reactions: Some chemical reactions release energy as infrared radiation, for example, during the combustion of fuels.
    • Electrical devices: Many electrical components, like incandescent bulbs and electronic circuits, can also emit infrared radiation due to heat generated during their operation.
  • The excited atom can transfer its energy to another atom through a collision. This can cause a chain reaction or lead to other physical or chemical reactions.
Other Forms of Radiation:
  • Sometimes, the energy release might not be in the form of visible light but in other types of radiation, like infrared radiation.
  • An excited atom is unstable and wants to return to its ground state. It does this by releasing the absorbed energy in different ways:
  • Here as examples of situations where atoms are heated to produce light:
    • In a hot gas, like the filament in an incandescent bulb, heating excites atoms, causing them to emit visible light, producing the characteristic glow.
    • In fluorescent lamps, UV radiation excites atoms in a gas, which then releases visible light through a different mechanism.
      • So in incandescent bulbs, the heat directly excites the atoms in the filament, causing them to release energy as visible light. This is a direct conversion from thermal energy to light.
      • With fluorescent bulbs, the process is more complex:
        • UV Excitation: Ultraviolet (UV) radiation from a separate source (typically an electrical discharge) excites atoms in a gas within the bulb.
        • Energy Transfer: These excited atoms don’t directly emit visible light. Instead, they transfer their energy to other atoms present in the gas, typically mercury atoms.
        • Visible Light Emission: The mercury atoms subsequently release their absorbed energy as visible light. This process involves specific energy levels and transitions within the mercury atoms.
  • When sunlight excites atoms in the atmosphere, it causes them to emit specific wavelengths of light, resulting in phenomena like the aurora borealis.