Chem2

• What is an atom?


  The smallest part of an element
• How many different elements are there approximately?

  About one hundred
• What are compounds formed from?

  Elements combined in chemical reactions
• What does "chemically combined" mean?

  Elements are bonded together
• What does "fixed proportions" refer to in compounds?

  Same ratio of elements in compounds
• What does a chemical formula indicate?

  The composition of a compound
• How do you name ionic compounds with two elements?

  Use the metal name and nonmetal's first syllable
• What is the name of the compound formed from iron and oxygen?

  Iron oxide
• How do you name a compound with three elements including oxygen?

  Use the first syllable of the nonmetal and add "ate"
• What is a mixture?

  Two or more substances not chemically combined
• How can mixtures be separated?

  By physical processes
• What is filtration used for?

  Separating insoluble solids from liquids
• What is the residue in filtration?

  The insoluble solid left on filter paper
• What is crystallization used for?

  Separating soluble solids from liquids
• How would you obtain a pure dry sample of salt?

  Use crystallization with heat
• What is simple distillation used for?

  Separating mixtures of liquids
• What is fractional distillation?

  Separating a mixture of liquids by boiling points
• What does chromatography analyze?

  Different components of a liquid mixture
• What are the parts of an atom?

  Protons, neutrons, and electrons
• Where are protons located in an atom?

  In the nucleus at the center
• What is the average size of an atom?

  About 0.1 nanometers
• What is the relative mass of an electron?

  Very small, not zero
• How do you calculate the number of protons, electrons, and neutrons from a periodic table square?

  Use atomic number and mass number
• What defines an element like carbon?

  It has six protons
• What are isotopes?

  Atoms with the same protons but different neutrons
• Why does chlorine have a mass of 35.5 on the periodic table?

  It has two stable isotopes
• How do you calculate the relative atomic mass of a sample with isotopes?

  Use the percentage and mass of each isotope
• What was Dalton's model of the atom?

  Atoms are indivisible spheres
• What did JJ Thompson discover about atoms?

  Atoms contain electrons
• What was Rutherford's contribution to atomic theory?

  Discovered the nucleus in atoms
• What did Niels Bohr propose about electrons?

  Electrons exist in distinct shells
• What is the modern atomic model composed of?

  Protons and neutrons in the nucleus
• How are elements arranged in the periodic table?

  By atomic number, number of protons
• What are groups in the periodic table?

  Columns of elements with similar properties
• Why is the periodic table called "periodic"?

  Properties occur at regular intervals
• What determines the chemical properties of elements in a group?

  The number of electrons in the outer shell
• How were elements originally arranged in the periodic table?

  According to atomic weight
• What problem arose from arranging elements by atomic weight?

  Some elements were incorrectly placed
• What is the significance of potassium and argon in the periodic table?

  They were incorrectly placed by atomic weight
• How many electrons are in the outer shell of an element that determines its reactivity?

  Three electrons