Protons

Proton: a subatomic particle found in the nucleus of every atom, carrying a positive electric charge. It has a mass of approximately 1.672×10⁻²⁷ kilograms, about 1836 times that of an electron. Protons are bound together by the strong nuclear force mediated by gluons. They determine the atomic number of an element and, along with neutrons, make up the atomic nucleus. Protons play a crucial role in the structure of atoms, chemical properties of elements, and processes such as nuclear fusion in stars. 

1.0Discovery of the Proton

The discovery of the proton and its mass involves several key historical experiments and developments:

1. Eugen Goldstein's Contribution:

In 1886, German physicist Eugen Goldstein conducted experiments using a modified cathode ray tube. He used a perforated cathode and observed some rays are travelling in the opposite direction of the cathode rays, which he named canal rays. These canal rays consisted of positively charged particles, and their properties varied depending on the type of gas used in the discharge tube. Goldstein's discovery of canal rays provided early evidence of positively charged particles in atoms, setting the stage for later discoveries.

• Positive Rays or Canal Rays Electrical discharge in the modified cathode ray tube revealed positively charged particles or canal rays. Key characteristics include:
• Nature Dependence: Unlike cathode rays, the positive particles depend on the gas in the tube, representing positively charged gaseous ions.
• Charge to Mass Ratio: The charge-to-mass ratio of these particles varies with the gas they originate from.
• Multiple Charges: Some particles carry multiples of the fundamental unit of electrical charge.
• Field Behavior: Positive Rays or Canal Rays behavior in magnetic or electric fields is opposite to that of electrons or cathode rays.

2. Discovery by Ernest Rutherford (1917):

• Experiment: Rutherford conducted experiments where he bombarded nitrogen gas with alpha particles and observed the emission of hydrogen nuclei.
• He concluded that the hydrogen nucleus, which he called a proton, was a fundamental particle. He identified the proton as a particle with a positive charge.

Mass Measurement and Mass Spectrometry

• Early measurements of atomic masses were done using chemical methods, which were not precise enough to distinguish the mass of individual protons.

Mass Spectrometry (1919)

Francis Aston developed the mass spectrometer, which allowed precise measurement of atomic masses. Aston’s work demonstrated that the masses of atoms were roughly integer multiples of the mass of the hydrogen atom, leading to the concept of atomic mass units (amu).

2.0Properties of a Proton

• Stability: Protons are stable particles. They do not decay under normal conditions and have an extremely long half-life.
• Composition: Protons are made up of of three quarks (two up quarks and one down quark) held together by the strong nuclear force, mediated by gluons.
• Interaction with Neutrons: Protons and neutrons are bound together in the atomic nucleus by the strong nuclear force, overcoming the electrostatic repulsion among the positively charged protons.
• Magnetic Moment: Protons have a magnetic moment, which means they can interact with magnetic fields. This property is exploited in techniques such as nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI).

3.0How to Calculate the Number of Protons in an Atom

To calculate the number of protons in an atom, simply find the element on the periodic table and find its atomic number. The atomic number equals the number of protons in the nucleus of an atom of that element. This fundamental property defines the element and its position in the periodic table.

For example:

4.0Proton in Chemical Reactions

Protons play a crucial role in acid-base chemistry, where they are transferred between molecules, influencing the pH and driving various chemical reactions. Protons are often represented as hydrogen ions (H⁺) in these reactions.

5.0Example Reactions Involving Protons

1. Acid-Base Reactions:

• Hydrochloric Acid (HCl) and Sodium Hydroxide (NaOH):          

   HCl+NaOH  →  NaCl+H₂O

In this reaction, HCl donates a proton (H⁺) to the hydroxide ion (OH⁻) from NaOH, forming water (H₂O) and sodium chloride (NaCl).

2. Buffer Systems:

• Acetic Acid (CH₃COOH) and Sodium Acetate (CH₃COONa):  

   CH₃COOH  ⇌  CH3COO⁻+H⁺

In a buffer solution, acetic acid can donate a proton to maintain pH balance when a base is added, and the acetate ion (CH₃COO⁻) can accept a proton when an acid is added.

3. Redox Reactions:

• Zinc and Hydrochloric Acid: 

   Zn + 2HCl  →  ZnCl₂ + H₂

Zinc (Zn) reacts with hydrochloric acid (HCl), where zinc displaces hydrogen, releasing hydrogen gas (H₂). The protons (H⁺) from HCl are reduced to form H₂.

4. Formation of Hydronium Ion:

• Water and Hydrogen Ion: 

    H₂O + H⁺  →  H₃O⁺

In aqueous solutions, a proton associates with a water (H₂O) molecule to form the hydronium ion (H₃O⁺), which is a crucial intermediate in many acid-base reactions.

5. Ammonia and Water:

• Formation of Ammonium Ion: 

   NH₃+H₂O  ⇌  NH₄⁺ + OH⁻

  Ammonia (NH₃) accepts a proton from water (H₂O) to form the ammonium ion (NH₄⁺) and a hydroxide ion (OH⁻).