science by student

  It came to him in a dream, Dmitri Mendeleev told a friend. He hadn’t slept for three days worrying how to classify the elements. Exhausted, he fell asleep and the answer came. Sadly, this may not be true. To begin with, Mendeleev –  born in Siberia in 1834 – had been thinking about the question since at least 1860, when the atomic weights of the elements had been established. By 1869 he was professor of chemistry at St Petersburg and writing a textbook for his students. Having finished the first section, he paused to consider which group of elements to cover next.  The answer may not have arrived in a dream, but it did come quickly, on 1 March 1869. Mendeleev had accepted an invitation to visit a cheese dairy that day. But instead, he turned over the dairy’s letter and scribbled on the back the atomic weights of dissimilar elements. Previously, chemists had sought a taxonomy through familial groups of elements; by comparing the unlike, Mendeleev could identify a general...

  The story begins in 1932 , with the discovery of the neutron by Sir James Chadwick, an English physicist.  Until 1932 , the atom was known to consist of a positively charged  nucleus  surrounded by enough negatively charged  electrons  to make the atom electrically neutral. Most of the atom was empty space, with its mass concentrated in a tiny nucleus. The nucleus was thought to contain both  protons  and electrons because the proton (otherwise known as the hydrogen ion, H + ) was the lightest known nucleus and because electrons were emitted by the nucleus in  beta decay . In addition to the beta particles, certain radioactive nuclei emitted positively charged  alpha particles  and neutral  gamma radiation. He was awarded the Nobel Prize🧪🧑‍🔬 in Physics in 1935 for this discovery. Chadwick's experiment involved bombarding beryllium with alpha particles from polonium. This resulted in the production of an uncharged, penetrat...

  Newton’s laws of motion , three statements describing the relations between the forces acting on a body and the   motion   of the body, first formulated by English physicist and mathematician   Isaac Newton , which are the foundation of classical   mechanics . Newton’s first law: the law of inertia Newton’s first law states that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a  force . In fact, in classical Newtonian mechanics, there is no important distinction between rest and  uniform motion  in a straight line; they may be regarded as the same state of motion seen by different observers, one moving at the same  velocity  as the particle and the other moving at constant velocity with respect to the particle. This  postulate  is known as the law of  inertia .

  Alpha particles were first described by  Ernest Rutherford in 1899 while studying radioactivity .  He initially identified two types of radiation, alpha and beta, and later, in 1907, he and Hans Geiger determined that alpha particles were essentially helium atoms stripped of their electrons, or doubly-ionized helium nuclei (He2+).  Rutherford's work, particularly his gold foil experiment, not only led to the discovery of the atomic nucleus but also provided a fundamental understanding of alpha particles and their role in radioactive decay, as noted by Britannica and the Nobel Prize website.   Initial Discovery: Rutherford's work in 1899, while investigating the properties of radioactive elements, led to the identification of two distinct types of radiation: alpha and beta.   Identifying Alpha Particles: Further research, particularly with Hans Geiger, revealed that alpha particles are essentially helium atoms that have lost their two outer electrons, maki...

The Electron was covered by  J.J.   Thomson in 1897 using a cathode ray discharge tube experiment .  His experiments, where he studied the properties of cathode rays, led him to conclude that they were streams of negatively charged particles, now known as electrons.  This discovery demonstrated that atoms are not indivisible, as previously believed, but are composed of smaller subatomic particles.   Elaboration: Cathode Ray Experiment: J.J.  Thomson's experiment involved passing electricity through a gas inside a sealed glass tube with two electrodes, one positive and one negative (cathode).   Cathode Rays: He observed that rays emitted from the cathode were deflected by electric and magnetic fields, indicating they were negatively charged.   Determining the Charge-to-Mass Ratio: Thomson measured the bending of the rays in different fields and determined the ratio of their charge to their mass, which was much lower than that of any known ion. ...

  The first antibiotic, penicillin, was discovered by Alexander Fleming in 1928   when he observed a mold, Penicillium notatum, inhibiting the growth of Staphylococcus  bacteria.  This accidental discovery sparked a new era of antibiotic development, leading to the widespread use of antibiotics and a significant decrease in deaths from bacterial infection. Fleming's Observation In 1928, while working with Staphylococcus bacteria at St. Mary's Hospital in London, Fleming noticed that a mold had contaminated one of his Petri dishes.  He observed that the mold had created a clear, bacteria-free zone around it, indicating that it was producing a substance that inhibited bacterial growth. Isolation and Identification:🧑‍🔬 Fleming isolated the mold and identified it as Penicillium notatum.  He then extracted a substance from the mold, which he named penicillin.   Early Research:🦠 Fleming published his findings in 1929 and determined that penicillin was eff...

  Discovery of the Cell Cells are the basic 'structural unit' of all living beings. They remained undiscovered for a long time because the majority of the cells are too small to be seen by the unaided eye. Robert Hooke was the first scientist who observed thin slices of cork (obtained from the bark of a tree) through his self-designed microscope , in 1665. He observed that they had honey-comb like structures consisting of little compartments (in Latin, 'cell' means 'a little room'). It was later explained that these 'compartments' were actually 'dead cells, bound by a 'cell wall'.  The cells have the same basic structure, but they are different, with respect to their number, shape and size, in different living organisms. Cell Number An Amoeba and an earthworm are of different sizes. This difference, in the size of the organism, is due to the number of cells present in them. While Amoeba is a living organism consisting of a single cell, an ear...

  The  Watson-Crick Model  of DNA (1953)  🧬🧪   Deoxyribonucleic Acid  ( DNA ) is a  double-stranded, helical molecule . It consists of two  sugar-phosphate backbones  on the outside, held together by  hydrogen bonds  between pairs of  nitrogenous bases  on the inside. The bases are of four types ( A ,  C ,  G , &  T ): pairing always occurs between  A  &   T , and  C   &   G .   James Watson   (1928 - )  and  Francis Crick   (1916 - 2004)  realized that these pairing rules meant that either strand contained all the  information  necessary to make a new copy of the entire molecule, and that the  aperiodic  order of bases might provide a  " genetic code " .      Watson and Crick  shared the  Nobel Prize in 1962   for their discovery, along with  Maurice Wilkins   (1916...

 The Bohr model is a historical model of the atom proposed by Niels Bohr in 1913 . It was a major advancement in understanding atomic structure, especially for hydrogen-like atoms. Here's a simple breakdown of the Bohr model: 🔬 Key Features of the Bohr Model Electrons orbit the nucleus in fixed circular paths called energy levels or shells . Each orbit has a specific energy associated with it, and electrons in the same orbit have the same energy . Electrons can jump between energy levels : When they absorb energy , they move to a higher level (excited state). When they release energy (usually as light), they fall to a lower level (ground state). The energy difference between the levels corresponds to the frequency of light emitted or absorbed: E = h ν E = h \nu where E E is energy, h h is Planck’s constant, and ν \nu is frequency. 🧪 Example: Hydrogen Atom The simplest Bohr atom is hydrogen (1 proton, 1 electron). Its electron orbits a...

   The history of scientific discoveries is a fascinating journey of exploration, observation, and experimentation that has shaped our understanding of the natural world. Here’s a brief overview of some of the most significant scientific discoveries that have revolutionized our understanding: 1.  The Theory of Gravity (Isaac Newton, 1687) Isaac Newton's formulation of the law of universal gravitation in his work  Principia  explained how objects are attracted to one another with a force that depends on their masses and the distance between them. This discovery not only helped us understand the motion of celestial bodies but also laid the foundation for classical mechanics. 2.  The Structure of the Atom (Early 20th Century) The discovery of the atom's structure marked a turning point in physics and chemistry. In 1911, Ernest Rutherford’s gold foil experiment revealed that atoms have a dense nucleus, and in 1913, Niels Bohr proposed a model where electrons or...