Reading the periodic table

• Periodic Table


  A chart that shows all the known elements
• There are over 100 known atoms — one for each of the known elements
• Atomic number


  The number of protons in the nucleus (which is the same as the number of electrons in the atom)
• Symbol


  A one or two letter symbol that represents the element. These internationally-used symbols are abbreviations for the common name or the Latin name of the element.
• Elements in the same row

  • Are in the same period, meaning they have similar physical properties, such as how well they bend or conduct electricity
• Elements in the same column

  • Are in the same group, meaning they react with other elements in similar ways
• The periodic table is a tabular array of the chemical elements organized by atomic number, from the element with the lowest atomic number, hydrogen, to the element with the highest atomic number, oganesson
• Atomic number


  The number of protons in the nucleus of an atom of that element
• Periodic table groups


  • Displayed as vertical columns numbered from 1 to 18
  • Elements in a group have very similar chemical properties, which arise from the number of valence electrons present
• The arrangement of the elements in the periodic table comes from the electronic configuration of the elements</b>
• Because of the Pauli exclusion principle, no more than two electrons can fill the same orbital
• The periodic table has two rows at the bottom that are usually split out from the main body of the table
• There is no scientific reason for this split, it is merely done to make the table more compact
• Periodic law


  The recurring pattern in the properties of elements when they are arranged in order of increasing atomic number
• Short-period form of periodic system of elements, 1930


  • Listing the elements known by 1930
  • At that time it was not clear that thorium (90), protactinium (91), and uranium (92) were part of the actinide series, and they were often placed in groups IVa, Va, and VIa, respectively, because they showed some similarities to hafnium (72), tantalum (73), and tungsten (74)
• With the discovery of the noble gases helium, neon, argon, krypton, radon, and xenon by Lord Rayleigh (John William Strutt) and Sir William Ramsay in 1894 and the following years, Mendeleev and others proposed that a new "zero" group to accommodate them be added to the periodic table
• Mendeleev was able to predict the existence, and many of the properties, of the then undiscovered elements eka-boron, eka-aluminum, and eka-silicon, now identified with the elements scandium, gallium, and germanium, respectively
• After the discovery of helium and argon, the periodic law permitted the prediction of the existence of neon, krypton, xenon, and radon
• Atomic number


  The ratio of the nuclear charge to that of the electron, which was noted to be roughly one-half the atomic weight
• The exact atomic weight of an element is of small significance for its position in the periodic system, as shown by the existence of isotopes of every element—atoms with the same atomic number but different atomic weights
• The chemical properties of the isotopes of an element are essentially the same, and all the isotopes of an element occupy the same place in the periodic system in spite of their differences in atomic weight
• Atom


  The basic unit of matter, consisting of a nucleus surrounded by electrons. The nucleus contains protons and neutrons, while the electrons orbit the nucleus in regions of space called orbitals.
• Nucleus


  The central part of an atom, containing protons and neutrons.
• Protons


  Positively charged particles found in the nucleus of an atom.
• Neutrons


  Neutral particles found in the nucleus of an atom.
• Electrons


  Negatively charged particles that orbit the nucleus of an atom. Electrons are arranged in energy levels and have a property called spin, which can be either "up" or "down".