Science

• an atom

  The smallest part of the element that can be identified as an element
• Atom


  • Includes a nucleus, filled with neutrons (neutral/no charge) and protons (have a positive charge (+1))
  • Around the nucleus there are electron (negative charge (-1)) shells that orbit at a fixed distance from the atom
• Isotopes


  Atoms of the same element that have different number of neutrons
• Ionic bonding


  • Occurs between metals (they tend to lose the electrons) and non-metals (they typically gain the electrons)
  • They TRANSFER the electrons
• Ionic compound characteristics

  • Have a crystal lattice structure, where the ions are arranged in a repeating three-dimensional structure
  • Have high melting and boiling points, due to the strong electrostatic force
  • Do not conduct electricity because the ions are fixed in place
  • Are soluble in water
• Covalent bonding


  • The electrons SHARE in the valence shell
  • Results in the formation of discrete molecules with specific shapes and sizes
  • There are single, double and triple bonds
• Covalent compoundscharacteristics


  • Have lower melting and boiling points due to a weaker intermolecular force
  • Do not conduct electricity because they do not have free ions or electrons
• 
  

  Nonpolar covalent compound Electrons are shared equally, dissolve in nonpolar solvents

• Atoms want to have a full shell (up to 8) so they want to either add or subtract the amount of electrons in their valence shell
• If an atom wants to lose an electron, they become more positively charged and they become a cation
• If an atom wants to gain an electron, they become more negatively charged and become an anion
• You can determine the number of electrons in the outer shell by looking at the atomic mass
• The Law of Conservation of Mass states that matter is neither created or destroyed. Instead, the atoms in use are simply rearranged into something new. The same number of atoms that were present at the start, at still present at the end.
• Exothermic reactions are reactions that produce energy and heat. Energy is EXITING, meaning the reaction is most likely hot
• Endothermic reactions are when reactions ABSORB energy and heat, meaning they are cold.
• Protons = atomic number

  Electrons = atomic number

  Neutrons = atomic mass - atomic number
• When you go left to right across the periodic table, you increase in ionization energy, electronegativity, and electron affinity
• As you go UP the periodic table, you increase in electronegativity, ionization energy and electron affinity
• As you go DOWN and RIGHT TO LEFT from the periodic table, you increase in atomic radius.
• pH measures the acidity or alkalinity of something. The neutral level is 7. If it is below 7, it is acid, if it is above 7, it is a base.
• ionization energy is the amount of energy required to remove a loose electron in the outer shell. The higher it is, the less reactive it tends to be.

  Low I.E= High reactivity

  Electronegativity is the tendency of an atom to attract electrons towards itself. Higher electronegativity results in higher reactivity
• periods are across

  groups are down (columns)
• The modern periodic table is arranged in order of increasing atomic number, with the same number of electrons in each group.
• covalent bonding looks like a sea of electrons floating around while the atoms stay still