The modern periodic table

• Who made an early periodic table?

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

  Elements are arranged in order of atomic number in periods and groups
• What are the horizontal rows in the periodic table called?

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

  Groups
• Why is the table called the periodic table?

  Because elements with similar properties occur at regular intervals
• What did Mendeleev not know about that explains pair reversals in his table?

  Mendeleev did not know about isotopes
• What is an isotope?

  Atoms of an element with the same number of protons and electrons but different numbers of neutrons
• Why were the positions of iodine and tellurium reversed in Mendeleev's table?

  Because iodine has one naturally occurring isotope, iodine-127, which is the most abundant
• What isotopes does tellurium have?

  Tellurium-128 and tellurium-130
• What gives tellurium a greater relative atomic mass compared to iodine?

  The 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 arranged in the modern periodic table?

  They are in the correct order based on their atomic numbers
• What is the structure of the modern periodic table?

  • Elements arranged in rows (periods) and columns (groups)
  • Ordered by increasing atomic number
  • Elements with similar properties in the same group
• What are the implications of isotopes on the arrangement of elements in the periodic table?

  • Isotopes can lead to pair reversals in early periodic tables
  • Understanding isotopes helps clarify the correct order of elements
  • Influences the relative atomic mass of elements