Basic Chemistry

• Protons have a positive charge
• Neutrons have a neutral charge
• Electrons have a negative charge
• Electrons are outside the nucleus
• Protons are inside the nucleus
• where are neutrons located?

  inside the nucleus
• atomic number (z)


  number of protons in the atom
• mass number (a)


  sum of protons and neutrons in the atom
• atomic number - protons = neutrons
• mass number - neutrons = atomic number
• Lewis dot diagrams

  Only show valence electrons
• Octet rule

  Other than first shell (2e), other shells are filled when they have 8 electrons
• Covalent bond


  shares electrons
• ionic bond


  one atom gives away an electron while another atom takes an electron, resulting in a pure charge
• nonpolar covalent bond


  sharing electrons equally, resulting in no charge
• electronegativity


  measure of how strongly an atom pulls electrons towards itself
• C-C

  nonpolar covalent bond
• C-H

  nonpolar covalent
• O-H


  polar covalent
• polar covalent bond


  sharing electrons but not equally, resulting in a partial charge
• losing electrons

  positive charge
• gaining electrons

  negative charge
• bohr diagram


  shows all shells and electrons
• valence electrons


  electrons in the outermost shell
• group number (vertical columns)

  tells number of valence electrons
• period number (horizontal rows)

  number of energy shells
• metals are in groups 1A and 2A (except hydrogen)
• nonmetals are in groups 3A to 8A
• noble gases are inert and chemically stable
• noble gases are in group 8
• halogens are in group 7
• isotopes have the same number of protons and different numbers of neutrons
• cations are positive
• anions are negative
• carbon can only make covalent bonds
• carbon can make up to 4 covalent bonds with other atoms
• EN difference less than or equal to 0.5

  nonpolar covalent
• EN difference between 0.5 and 1.7

  polar covalent
• EN difference greater than 2.0

  ionic
• if the EN is between 1.7 and 2.0 and a metal is involved, the bond is ionic