chem 1

• What is a compound?

  A substance with two or more different atoms bonded
• What is the chemical formula for water?

  H2O
• How many hydrogen atoms are in one water molecule?

  Two hydrogen atoms
• What must be true about the number of atoms in a chemical reaction?

  They must be the same on both sides
• What is the first step in balancing a chemical equation?

  Start with atoms only in compounds
• Why can't we change small numbers in a chemical formula when balancing?

  It would change the compound's identity
• What is a mixture?

  A combination of elements and compounds not bonded
• How can you separate sand from water?

  Using filtration
• What is crystallization used for?

  To separate a solute from a solvent
• What is fractional distillation used for?

  To separate liquids with different boiling points
• What are the three main states of matter?

  Solid, liquid, gas
• How do particles behave in a solid?

  They vibrate around fixed positions
• What happens to particles when a substance melts?

  They gain energy and move more freely
• What do state symbols indicate in chemical equations?

  The state of substances: solid, liquid, gas
• Who proposed the plum pudding model of the atom?

  JJ Thompson
• What did Rutherford discover about the atom?

  It has a small, dense nucleus
• What are protons and neutrons collectively called?

  Nucleons
• What is the charge of a neutron?

  Zero
• What does the atomic number represent?

  The number of protons in the nucleus
• What happens when an atom gains or loses electrons?

  It becomes an ion
• What is the mass number of an atom?

  The total number of protons and neutrons
• What are isotopes?

  Atoms of the same element with different neutrons
• How is the average relative atomic mass calculated?

  By averaging the masses of isotopes
• Who created the modern periodic table?

  Dmitri Mendeleev
• What do the groups in the periodic table indicate?

  The number of electrons in the outer shell
• What are alkali metals?

  Group one metals with one outer electron
• How does reactivity change in alkali metals down the group?

  It increases as you go down
• What are halogens?

  Group seven elements needing one electron
• How does reactivity change in halogens down the group?

  It decreases as you go down
• What are noble gases known for?

  Being very unreactive
• What happens to metals when they lose electrons?

  They become positively charged ions
• What is the charge of group one metal ions?

  One plus
• What is ionic bonding?

  Transfer of electrons between atoms
• What must the charges of ions in an ionic compound do?

  Add up to zero
• What is the structure of ionic compounds?

  They form a lattice structure
• Why can ionic compounds conduct electricity when molten or dissolved?

  Because ions are free to move
• What is covalent bonding?

  Sharing of electrons between non-metals
• What is a simple molecular structure?

  Individual molecules with weak intermolecular forces
• What is a giant covalent structure?

  A large network of covalently bonded atoms
• How does graphite conduct electricity?

  Due to delocalized electrons between layers