NS2

• The origin of all the naturally occurring elements fall into two phases: Big Bang or Primordial Nucleosynthesis and Stellar Nucleosynthesis.
• The "light" elements, such as Hydrogen (H), Helium (He), and small amounts of lithium (Li) and beryllium (Be), were present during the initial formation of the universe.
• Nucleosynthesis is the process that creates new atomic nucleus from pre-existing nucleons, which is proton and neutrons.
• The formation of heavy elements by fusion of lighter nuclei in the interior of stars is known as stellar nucleosynthesis.
• The density inside a star is great enough to sustain fusion for extended time periods required to synthesize heavy elements.
• There are many nuclear synthetic pathways or nuclear fusions to produce heavy elements, including Proton-proton fusion, Carbon-Nitrogen-oxygen cycle, and Triple alpha process.
• Layers near core of stars have very high temperatures enough to nucleosynthesize heavy elements such as silicon and iron.
• Heavy elements cannot be formed through fusion as tremendous amounts of energy are needed for the reaction to occur.
• In a neutron capture reaction, heavy elements are created by addition of more neutrons to existing nuclei instead of fusion of light nuclei.
• Heavy elements are formed in a supernova, a massive explosion of a star.
• The concept of Atomic Number led to the synthesis of new elements in the laboratory.
• Alpha particles have atomic number of 2 and atomic mass of 4.
• Neutron has 0 atomic number and 1 atomic mass.
• Technetium is the first artificial element.
• Discoveries resulted in a more accurate positioning of elements in the Periodic Table by closer determination of atomic numbers.
• Democritus introduced the idea of atom as the basic building block of all matter, known for the word “atomos” which means “uncuttable/indivisible” in Greek.
• Democritus’ idea of the atom has been called “the best guess in antiquity” as it was correct in many ways, yet it was based on pure speculation.
• Different elements differ in their numbers of protons and electrons and this gives them different physical and chemical properties.
• Democritus believed that different kinds of atoms make up different types of matter.
• Democritus suggested that sweet substances are made of smooth atoms and bitter substances are made of sharp atoms.
• Democritus speculated that atoms of liquids are slippery, which allows them to slide over each other and liquids to flow.
• Democritus believed that atoms of solids stick together.
• Aristotle’s opinion was accepted for more than 2000 years, and Democritus’ idea was more or less forgotten.
• John Dalton developed an entire theory about the atom, much of which is still accepted today.
• The idea of the atom was revived around 1800 by the English scientist John Dalton.
• The majority of Greeks believed that the smallest unit that anything could be divided into was the element.
• Empedocles proposed that everything was made up of a mixture of the four elements, and proposed a simple experiment to prove his point.
• Empedocles set light to a stick, and since the stick burns, it obviously contains fire.
• A dirty residue is left behind once the stick has burnt, so the stick also contains earth.
• The residue is damp, so water must be present.
• The burning stick gives off smoke, and thus air is in there too.
• Aristotle’s theory of matter has been proven wrong.
• There were long periods of acceptance of false ideas and concepts designed by a man who made many observations and theories which lead to great progress.
• Alchemical Elements: Alchemy, the medieval forerunner of chemistry, was concerned particularly with attempts to convert base metals into gold or to find a universal elixir.
• PROTON </flashcard
• Building block of chemistry
• + and - REPEL ATTRACT
• A property which defines the force that a particle will exert on other charged particles.
• composed of 3 sub-atomic particles
• The CORE of chemistry