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• Nuclear Reactions

  • Reactions that involve the nucleus or nuclei of atoms
  • Processes in which a nucleus either splits into smaller nuclei (nuclear fission) or combines with another nucleus (nuclear fusion)
• Nuclear Fusion

  Combination of nuclei into heavier nucleus
• Isotopes

  Atoms of the same element with different numbers of neutrons in their nuclei
• Mass number

  Number of protons + number of neutrons
• Atomic number

  Number of protons
• Subatomic particles

  • Electron (negative charge)
  • Proton (positive charge)
  • Neutron (no charge)
  • Alpha particle (high-speed particle consisting of 2 proton and 2 neutron)
  • Beta particles (high-speed electron)
  • Gamma ray (high-speed stream of proton)
  • Positron (positive-charged electron)

  
• Edwin Hubble

  • He explained that the universe is expanding which is the first evidence of the Big Bang
  • Stars and galaxies shines with the light shifted toward the red end of the visible spectrum. This phenomenon is called redshift
  • The size of the redshift is proportional to the distance and speed of as star that is moving away from the Earth
• Big bang theory

  • Explain the universe, together with space, time and matter started from a singularity that is an extremely hot and very dense point 14 million years ago
  • Explain how the elements were initially form the formation different elements involved many nuclear reactions including fusion, fission and radioactive decay
  • But there is "No Explosion" during this event, so the scientists agreed on the immediate expansion of the universe in less than a second which is called inflation
  • As the expanding universe cooled, the proton and neutron started to fuse (combine)to form heavier nuclei of deuterium (an isotope of Hydrogen with one neutron and one proton) and some into Helium

  
• Stellar Formation and Evolution

  1. The universe continuously expanded for several years, and the cloud of Hydrogen and helium gases condensed to form stars, including the Sun

  2. Over millions of years, nuclear reactions continued, which produced elements heavier than Lithium

  3. The light elements combined to form atoms of Carbon, Neon, Oxygen, Silicon and Iron

  4. Younger yellow stars made up of hydrogen were fueled by the energy released from the fusion of hydrogen nuclei to form helium

  5. In the outer layer of a yellow star, the burning of hydrogen through nuclear fusion produced helium

  6. Once enough 4/2 He , these nuclei becomes concentrated at the core of the star, making the temperature hotter at that region

  7. Hydrogen fusion continued, but in a shell surrounding the helium core
• Stellar Explosion

  1. As the red giant star exhausted the nuclear fuel of light elements, its core started to collapse that eventually led to the explosion of the star. This explosion called Supernova released a huge amount of nuclear energy and produced, through neutron capture and radioactive decay, and other heavier elements than Iron

  2. Neutron reaction were either as fast as a fraction of a second or as slow as a few million years

  3. Slow neutron capture (s-process)

  4. Rapid neutron capture (r-process)

  5. These process occurred as a seed nucleus captured neutrons, forming a heavier isotopes of the elements that was either stable or radioactive

  6. Stable isotopes continued to capture neutrons and formed other heavier isotopes of the seed nuclei

  7. Radioactive Isotopes however underwent to beta decay, producing an isotopes of a new elements

  
• Periodic Table of Elements

  • Contains naturally occurring elements as well as artificial or synthetic ones
• Lewis dot symbol

  • It consist the symbols of element (representing its nucleus and inner electrons) surrounded by one or more dots: each dots corresponds to every valence electron in an atom of the elements
  • Valence electrons are the electrons in the highest occupied energy level of the atom
  • Valence electrons are the only electrons generally involved in bond formation
• Types of Intramolecular Forces

  • Ionic bonds
  • Covalent bonds
  • Metallic bonds
• Ionic Bond

  • It is due to the attraction between a cation and anions
  • Cations are produced when metal lose their electron and gain a positive charge
  • Anions are created by gaining electrons by non-metals that provides them negative charge
  • Substances that contains atom bounds by the ionic bonds are called Ionic Compounds
• Covalent Compound

  • It exist when two non-metals share electrons to attain stability as required by octet rule
  • Covalent compounds could have single or multiple bonds, depending on the elements involved in the attraction
• Polarity of Covalent Bond

  • The property of polarity consists of the distribution of charge throughout a molecule or compound
  • A bond is considered non polar when its electrons are equally shared throughout a molecule, resulting in an even distribution of charges
• Electronegativity

  Defined as an atom's ability to attract electrons towards it in a chemical bond
• Electronegativity Trends

  • From left to right across the period table electronegativity increases. This is because of the increased number of protons as the atomic number increase
  • From top to bottom electronegativity decreases because of the increasing size of the atoms
• Electronegativity and Bond Type

  The absolute value of the difference in electronegativity (ΔEN) of two bonded atoms provides a rough measure of the polarity to be expected in the bond and, thus, the bond type
• Metallic Bond

  The absolute value of the difference in electronegativity (ΔEN) of two bonded atoms provides a rough measure of the polarity to be expected in the bond and, thus, the bond type
• Metallic bonding and metal properties

  • High electrical and thermal conductivity: Free electrons are charge carries in electric conductivity and thermal energy (heat) carriers in thermal conductivity
  • High melting and boiling points: Strong attractive forces between delocalized electrons and atomic nuclei give metals high melting and boiling points
  • Malleability and ductility: Metallic bonding accounts for metal mechanical properties, including malleability and ductility. Because electrons slide past each other, it's possible to hammer metals into sheets (malleability) and draw them into wires (ductility)
  • Metallic luster: Delocalized electrons reflect most light, giving metals a shiny appearance
  • Silver color: Most metals appear silver because most light is reflected off the oscillating resonance electrons (surface plasmons). Absorbed light tends to be in the ultraviolet part of the spectrum, which is outside the visible range. In copper and gold, the absorbed light is within the visible range, giving these metals a reddish and yellowish color
• Intermolecular Forces

  Physical Properties are characteristics of matter that are observed without changing its chemical composition. They are attributed to the forces of attraction that exist between molecules that comprise matter. These forces are termed Intermolecular forces (IMFA)
• Dipole - Dipole Force

  These forces occur when the partially positively charged part of a molecule interacts with the partially negatively charged part of the neighboring molecule
• Hydrogen Bonding

  This is a special kind of dipole-dipole interaction that occurs specifically between a hydrogen atom bonded to either an oxygen, nitrogen, or fluorine atom
• London Dipersion Forces, Under the category of van der waal forces

  These are the weakest of the intermolecular forces and exist between all types of molecules, whether ionic or covalent—polar or nonpolar
• Effects of Intermolecular Forces

  • The intermolecular forces are associated with the observable properties of various substances. The physical properties of molecules depend upon the type and strength of their intermolecular forces of attraction. These properties are solubility, melting point, boiling point, surface tension, viscosity, capillary action, and evaporation rate
  • When it comes to solubility, the solute and the solvent mix when they both exhibit the same intermolecular forces of attraction
  • The melting and boiling points of substances with stronger IMFA are higher compared to those with weaker IMFA
  • In the case of surface tension, molecules with stronger intermolecular forces of attraction will exert greater cohesive forces and acquire less surface area (higher surface tension) than those with weaker IMFA
  • Viscosity is also affected by intermolecular forces
• Democritus

  • This is the Greek philosopher Democritus who began the search for a description of matter more than 2400 years ago
  • To Democritus, atoms were small, hard particles that were all made of the same material but were different shapes and sizes
  • Atoms were infinite in number, always moving and capable of joining together
• Dalton's Model

  • In the early 1800s, the English Chemist John Dalton performed a number of experiments that eventually led to the acceptance of the idea of atoms
  • He deduced that all elements are composed of atoms. Atoms are indivisible and indestructible particles
  • Atoms of the same element are exactly alike
  • Atoms of different elements are different
  • Compounds are formed by the joining of atoms of two or more elements
• Thomson's Plum Pudding Model

  • He proposed a model of the atom that is sometimes called the "Plum Pudding" model
  • Atoms were made from a positively charged substance with negatively charged electrons scattered about, like raisins in a pudding
  • Thomson studied the passage of an electric current through a gas
  • As the current passed through the gas, it gave off rays of negatively charged particles
• Rutherfords Gold Foil Experiment

  • Most of the positively charged "bullets" passed right through the gold atoms in the sheet of gold foil without changing course at all
  • Some of the positively charged "bullets," however, did bounce away from the gold sheet as if they had hit something solid. He knew that positive charges repel positive charges
  • Rutherford reasoned that all of an atom's positively charged particles were contained in the nucleus. The negatively charged particles were scattered outside the nucleus around the atom's edge
• Bohr Model

  • In 1913, the Danish scientist Niels Bohr proposed an improvement. In his model, he placed each electron in a specific energy level
• The wave model

  • According to the theory of wave mechanics, electrons do not move about an atom in a definite path, like the planets around the sun
  • In fact, it is impossible to determine the exact location of an electron. The probable location of an electron is based on how much energy the electron has
  • According to the modern atomic model, at atom has a small positively charged nucleus surrounded by a large region in which there are enough electrons to make an atom neutral

  
• Electron Cloud

  • A space in which electrons are likely to be found
  • Electrons whirl about the nucleus billions of times in one second
  • They are not moving around in random patterns
  • Location of electrons depends upon how much energy the electron has
• Dalton's Theory

  • He deduced that all elements are composed of atoms. Atoms are indivisible and indestructible particles
  • Atoms of the same element are exactly alike
  • Atoms of different elements are different
  • Compounds are formed by the joining of atoms of two or more elements
• J.J. Thompson's Model of Atom

  • Plum Pudding Model, 1896
  • Thought an atom was like plum pudding
  • Dough was Raisins