Unit 3

• Matter


  Substance that exists in physical form and has mass; a solid, liquid, or gas
• Atom


  Smallest unit of matter that forms an element and posses the characteristics or properties of that element
• Element


  Cannot be divided by chemical means
• Particle

  Smallest particle of an element
• Isotope


  Atoms that have the same atomic number and the same chemical properties; made entirely from of one type of atom
• Isotope


  • Carbon
• Molecule


  Two of more atoms of various elements that are combined to form structures that are held together by a chemical bond
• Compound


  Smallest part of a compound
• Compound


  • Water molecule has 3 atoms: 2 elements of Hydrogen and one element of Oxygen to form 1 molecule of water (2H + O = H2O)
• Substance


  Substance composed of identical molecules; any quantity of one type of molecule
• Substance


  • Baking soda (NaHCO3) is composed of molecules of salt (NaCl) and bicarbonate (HCO3)
• History of the atom

  • Greek
  • Dalton
  • Thompson
  • Rutherford
  • Bohr
  • Schrodinger
  • Mendeleev
• Greek Philosophers


  • First to use the term atom
  • Leucippus – earliest known atomic theory
  • Democritus of Abdera – Credited with formalizing the earliest atomic theory
  • 4 different atoms representing air, fire, earth and water
• John Dalton


  • English school teacher and physicist
  • All atoms in an element are identical
  • Atoms formed elements by a series of "Hooks and Eyes"
  • Explained an element was composed of tiny particles of identical atoms
• J.J. Thompson


  • British physicist
  • Discovered the electron
  • Studying the glowing stream visible when current was passed thru a cathode ray tube
  • Investigated and theorized the glowing particles were negatively charged particles of atoms
  • Described the "Plum Pudding" model of the atom where the plums were the electrons
  • The Nobel Prize in Physics 1906
• Ernest Rutherford


  • New Zealand physicist
  • Thompsons' student; conducting experiments with alpha particles
  • Introduced the "Nuclear" model of the atom
  • A small, dense, positively charged center surrounded by a negative cloud of electrons
  • Called the center of the atom the nucleus
  • The Nobel Prize in Chemistry 1908
• Niels Bohr


  • Danish physicist and philosopher
  • Introduced miniature "Solar System" model of the atom
  • Stated atoms composed of electrons, protons and neutrons
  • Determined electrons revolve around the nucleus in fixed, defined orbits or energy levels
  • The Nobel Prize in Physics 1922
• Erwin Schrödinger


  • Austrian physicist
  • Theorized that the behavior of electrons within atoms could be explained by treating them mathematically as matter waves
  • Contributed to the Quantum Mechanical Model of the atom
  • Uses the de Broglie wavelength, the Schrödinger equation, and the Heisenberg uncertainty principle
  • The Nobel Prize in Physics 1933
• Dimitri Mendeleev


  • Russian Chemist
  • Created the Periodic Table of Elements
  • Explained that elements are arranged in order of increasing atomic number
  • Organized the 65 known elements into 8 groups
• Periodic Table of Elements

  • 118 elements
  • 94 Naturally occurring elements (1 – 94) – Occur in nature
  • 24 Synthesized elements (95 – 118)
• Periodic Table of Elements

  • 8 Groups are arranged in vertical columns
  • Elements in each group have the same number of outer shell electrons
  • Elements reacts the same chemically
  • Group I – Alkali Metals
  • Group II – Alkaline Earth Metals
  • Group III – Boron Group
  • Group IV – Carbon Group
  • Group V – Nitrogen Group
  • Group VI – Oxygen Group
  • Group VII – Halogens
  • Group VIII – Nobel gases
• Inner transitional metals


  • Elements 57 to 71 and 89 to 103 that do not fit into the eight groups
  • Two series of elements not shown on a simplified periodic table
  • Generally have special qualities
  • Many are radioactive
• Periodic Table of Elements

  • 7 Periods are arranged in horizontal rows
  • Arranged in increasing order by atomic number
  • Period 1 – Two Elements
  • Period 2 – Eight Elements
  • Period 3 – Eight Elements
  • Period 4 – Eighteen Elements
  • Period 5 – Eighteen Elements
  • Period 6 – Thirty-two Elements
  • Period 7 – Thirty-two Elements
• Proton


  Positively charged particle
• Neutron


  Neutral particle (No charge)
• Protons & Neutrons


  • Contained in the nucleus of an atom called nucleons
  • Made of quarks bound together by gluons
• Electron


  • Negatively charged particle
  • Bound in energy levels called shells
  • Revolve around the nucleus
• Atomic Structure


  • The nucleus contains most of the atom's mass
  • The number of protons determines the chemical element or the atom's identity
  • Atoms are composed mostly of empty space
  • Normally atoms are neutral and have zero electric charge
  • Number of electrons equals the number of protons
• Ionized atoms


  Atoms that have had an electron added or removed
• Ionization


  Removal of an electron from its orbit around a nucleus
• Ion


  An atom that has lost or gained one or more electrons
• In most atoms, the number of neutrons is always greater than the number of protons
• Electrons can only exist in the orbital shells that surround the nucleus
• Electron shells names/symbol


  • K shell – 1st or inner shell; can contain no more than 2 electrons
  • L shell – 2nd shell
  • M shell – 3rd shell
  • N shell – 4th shell
  • O shell – 5th shell
  • P shell – 6th shell
  • Q shell – 7th shell
• Electron Arrangement


  • Each electron shell represents a different level of electron binding energy
  • The closer the electron to the nucleus, the more tightly bound the electron is in the shell, the higher the electron binding energy
  • K shell electrons have the highest binding energies
• Octet Rule


  The outermost shell of any atom can hold a maximum of 8 electrons
• Electron Arrangement


  1. 2n^2

  2. Limit of electrons in each shell is determined by the principle quantum number (n) which is the shell number

  3. Maximum number of electrons that can exist in each shell is calculated using: 2n^2
• 50 electrons can exist in the O shell
• Atomic Number


  • Number of protons in the nucleus of an atom
  • Represented by Z and referred to as an element's "Z number"
• Atomic Mass Number


  • Number of protons and neutrons in the nucleus of an atom
  • Symbolized by A and referred to as an element's "A number"
  • The atomic mass number is a whole number
  • The precise mass of an atom is called the atomic mass unit (amu) and is rarely a whole number
  • The atomic mass number ≠ atomic mass unit