Science 1

• Dobereiner's Triads


  Proposed by Johann Wolfgang Dobereiner in 1828 - The atomic mass of the middle element was almost equal to the average of the atomic masses of the first and the third elements.
• Law of Octaves


  Proposed by John Alexander Rreina Newlands in 1865 - According to him, when elements were arranged according to their atomic weights, every eighth element had properties similar to each other.
• Early Periodic Table of Elements

  1. Dmitry Ivanovich Mendeleev in 1869 arranged the elements according to their atomic mass.

  2. Lothar Meyer arranged the elements according to their atomic volume

  
• Mendeleev's law


  The physical and chemical properties of elements are a periodic function of their atomic masses.
• Periodic Law
• Modern Periodic Table


  • It shows the basic information about the elements.
  • The information you can get from this table can be used to predict physical and chemical properties of the elements.
  • This may also predict the properties of elements that may be possibly discovered.

  
• Periods


  • There are 7 periods.
  • It shows the number of energy levels the atom of each element has.
• Groups

  • 3 Main groups:
  • Group A – Representative elements (1,2, 13-18)
  • Group B – Transition elements (3-12)
  • Inner Transition elements – Lanthanides and Actinides
  • IUPAC Grouping (1-18)
• Representative Elements

  • 1 (1A) – Alkali Metals
  • 2 (2A)– Alkaline Earth Metals
  • 13 (3A) – Boron Group
  • 14 (4A)– Carbon Group
  • 15 (5A)– Nitrogen Group
  • 16 (6A)– Chalcogens
  • 17 (7A)– Halogens
  • 18 (8A)– Noble Gases
• Blocks

  • s block – Groups 1 and 2 (Sublevel S contains 2 electrons)
  • p block – Group 13-18 (Sublevel p contains 6 electrons)
  • d block – all transition elements (Sublevel d contains 10 e)
  • f block – all inner transition elements (Sublevel f contains 14 e)
• Atomic Radius


  It is one-half the distance between the nuclei of identical atoms that are bonded together.
• Ionic Radius


  An atom that either gains or loses electrons.

  Cation - an ion that loses electrons

  Anion - an ion that gains electrons

  Ionization - the process of an atom losing or gaining electrons
• Ionization Energy


  The energy required to remove an electron from an atom

  It measures how tightly bound an electron is to an atom

  LOW ionization energy = easy removal of electrons

  Ionization energy is always positive.
• Ionization Energy


  Left to right within a period, increases

  Top to bottom within a group, decreases
• Electron Affinity


  The amount of energy released or absorbed when an electron is added to an atom to form a negative ion.

  It is the measure of the atom's tendency to form ANION.

  Left to right – increases

  Top to bottom - decreases
• Electronegativity


  The ability of an atom to attract electrons.

  Left to right (within period) – increases

  Top to bottom (Within a group) - decreases
• Metallic Character

  METALS – left side of the "staircase" except Hydrogen

  METALLOIDS – within the "staircase"

  NONMETTALS – right side of the "staircase" with Hydrogen
• Elements in the Human Body

  • Aluminum
  • Iodine
  • Silicon
  • Boron
  • Iron
  • Silver
  • Calcium
  • Magnesium
  • Sodium
  • Chromium
  • Manganese
  • Zinc
  • Cobalt
  • Neon
  • Copper
  • Nitrogen
  • Fluorine
  • Oxygen
  • Gold
  • Potassium
  • Hydrogen
  • Selenium