chem

• the more electrons an atom has, the greater its attraction to other atoms
• ionic bonding is when metals react with non-metals to form ionic compounds
• in ionic bonds, metal loses electrons to become positively charged cations (e.g. Na+)
• covalent bonding occurs between two non-metals
• covalent bonding occurs between two non-metals where they share pairs of electrons
• molecules are formed from covalently bonded atoms
• when two non-metals share electrons they are called covalently bonded
• when two non-metals share electrons they are called molecules
• non-metal gains electrons to become negatively charged anions (e.g. Cl-)
• molecular formula shows how many atoms of each element there are in one molecule
• hydrogen bonding is weak intermolecular forces that occur between hydrogen and another element such as oxygen or nitrogen
• Substances are made of atoms, which are represented in the periodic table by a symbol
• Compound


  A substance that contains two or more different types of atoms chemically bonded together
• If there's no number after a symbol, there's an invisible 1
• Chemical reaction


  Atoms change what they're bonded to and how they're bonded
• Word equation


  A representation of a chemical reaction using words
• Chemical equation


  A representation of a chemical reaction using symbols
• Atoms are not created or destroyed in a chemical reaction, so the same number of each type of atom must be on both sides of the equation</b>
• Balancing a chemical equation

  Start with atoms only in compounds, then balance elements
• Mixture


  Any combination of different types of elements and compounds that aren't chemically bonded together
• Mixtures


  • Air
  • Salt water
• Solution


  A mixture of a solute dissolved in a solvent
• Separating mixtures


  1. Filtration

  2. Crystallization

  3. Distillation
• Physical processes


  • No new substances are being made
• States of matter


  • Solid
  • Liquid
  • Gas
• Melting and evaporation are physical changes, not chemical reactions
• Discovered atoms are made of positive and negative charges


  JJ Thompson
• Discovered the positive charge is in a small nucleus, with electrons orbiting relatively far away


  Ernest Rutherford
• Discovered electrons exist in shells or orbitals

  Niels Bohr
• Discovered the nucleus contains neutral charges called neutrons


  James Chadwick
• Protons and neutrons


  Have a relative mass of 1, electrons have a very small mass
• Atomic number


  The number of protons in the nucleus
• Mass number


  The total number of protons and neutrons in the nucleus
• Isotopes


  Atoms of the same element with different numbers of neutrons
• Relative abundance


  The percentage of each isotope in a sample
• The periodic table was originally ordered by atomic weight, then rearranged by Mendeleev based on chemical properties
• Electron shells


  Electrons exist in shells around the nucleus, with a maximum number in each shell
• Metals


  Elements to the left of the staircase on the periodic table, which donate electrons
• Non-metals


  Elements to the right of the staircase on the periodic table, which accept electrons
• Group


  The column an element is in on the periodic table, indicating the number of electrons in the outer shell