The periodic table

• Who published the first periodic table of elements?

  Dmitri Mendeleev
• What was Mendeleev's goal in organizing elements?

  To find ways to organize known elements
• In what year did Mendeleev publish his periodic table?

  1869
• How are elements arranged in the modern periodic table?

  By atomic number in periods and groups
• What do electronic configurations model?

  How electrons are arranged in atoms
• What is relative atomic mass?

  Mean relative mass of isotopes in an element
• What did Mendeleev note about the elements' properties?

  They showed a periodic trend
• What is a chemical property?

  How a substance reacts with others
• How did Mendeleev arrange elements with similar properties?

  By placing them in groups below each other
• What did Mendeleev do to classify elements effectively?

  Left gaps for undiscovered elements
• Why did Mendeleev switch the order of some elements?

  To keep groups consistent
• What did Mendeleev predict using gaps in his table?

  Properties of undiscovered elements
• What was the name of the element Mendeleev predicted next to silicon?

  eka-silicon
• Which element was discovered that confirmed Mendeleev's prediction?

  Germanium
• What is a pair reversal in Mendeleev's table?

  When elements are swapped for consistency
• Which element has a lower relative atomic mass than tellurium?

  Iodine
• Why did Mendeleev place iodine after tellurium?

  To align it with chlorine and bromine
• How did Mendeleev's approach to the periodic table differ from modern methods?

  He prioritized chemical properties over atomic mass
• Who made an early periodic table?

  Mendeleev
• How are elements arranged in the modern periodic table?

  By atomic number in periods and groups
• What do electronic configurations model?

  Arrangement of electrons in atoms
• What is the atomic number of an element?

  Number of protons in the nucleus
• What is another name for atomic number?

  Proton number
• What is the nucleus of an atom composed of?

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

  By atomic number, not relative atomic mass
• What are rows in the periodic table called?

  Periods
• What are vertical columns in the periodic table called?

  Groups
• What do elements in the same group have in common?

  Similar chemical properties
• Where are metals located in the periodic table?

  Left-hand side
• Where are non-metals located in the periodic table?

  Right-hand side
• What separates metals from non-metals in the periodic table?

  A zig-zag line starting at B-Al-Si
• What did Mendeleev not know about that explains pair reversals?

  Isotopes
• Why were iodine and tellurium's positions reversed in Mendeleev's table?

  Iodine has one naturally occurring isotope
• What is the most abundant isotope of iodine?

  Iodine-127
• What isotopes does tellurium have?

  Tellurium-128 and tellurium-130
• Why does tellurium have a greater relative atomic mass?

  High relative abundance of its isotopes
• What is the atomic number of tellurium?

  52
• What is the atomic number of iodine?

  53
• How are iodine and tellurium ordered in the modern periodic table?

  In correct order by atomic number
• Who made an early periodic table?

  Mendeleev