The periodic table

• Who made an early periodic table?

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

  Elements are arranged in order of atomic number in periods and groups
• What do electronic structures model in chemistry?

  They model how electrons are arranged in atoms
• What is the definition of a substance made of one type of atom only?

  • An element
• What is the atomic weight of an element equivalent to?

  It is equivalent to its relative atomic mass
• What was a limitation of early periodic tables?

  They were incomplete and had unknown elements
• Why were some elements placed in incorrect groups in early periodic tables?

  Because they were arranged by atomic weights, not properties
• In what year did Mendeleev publish his first periodic table?

  1869
• What did Mendeleev consider when arranging his periodic table?

  He considered the properties of the elements and their compounds
• What was the significance of the gaps Mendeleev left in his periodic table?

  They allowed him to predict the properties of undiscovered elements
• What was the name of the element Mendeleev predicted that was later discovered?

  Germanium
• How did Mendeleev handle the placement of iodine and tellurium in his table?

  He swapped their positions to align iodine with similar elements
• 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 is the atomic weight of iodine compared to tellurium?

  Iodine has a lower atomic weight than tellurium
• What is the definition of atomic number?

  The number of protons in the nucleus of an atom
• Why did Mendeleev prioritize chemical properties over atomic weights for some elements?

  To ensure elements with similar properties were grouped together
• What are periods in the periodic table?

  Horizontal rows in the periodic table
• What are groups in the periodic table?

  Vertical columns containing elements with similar chemical properties
• Why is the table called the periodic table?

  Because elements with similar properties occur at regular intervals
• What are the key features of Mendeleev's periodic table?

  • Arranged elements by increasing atomic weights
  • Left gaps for undiscovered elements
  • Grouped elements with similar chemical properties
  • Made predictions about properties of missing elements
• What did Mendeleev not know about that affected his periodic table?

  He did not know about isotopes
• What explains the pair reversals in Mendeleev's table?

  The existence of isotopes
• What is the most abundant isotope of iodine?

  iodine-127
• What isotopes are associated with tellurium?

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

  Due to the high relative abundance of its isotopes
• What are the atomic numbers of tellurium and iodine?

  Tellurium is 52 and iodine is 53
• How are iodine and tellurium positioned 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?

  • Arranged in rows (periods) and columns (groups)
  • Elements ordered by increasing atomic number
  • Similar properties occur at regular intervals
• What are the implications of isotopes on Mendeleev's periodic table?

  • Isotopes explain pair reversals
  • Affects the relative atomic mass of elements
  • Highlights the need for a modern understanding of atomic structure
• 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 do electronic structures model?

  They model how electrons are arranged in atoms
• What is the definition of an atom?

  • The smallest part of an element that can exist
• What is the nucleus of an atom?

  The central part of an atom containing protons and neutrons
• What do different shells in an atom hold?

  Different shells can hold different maximum numbers of electrons
• How do electrons occupy energy levels in an atom?

  Electrons occupy the lowest available energy level first
• What is the maximum number of electrons in the first shell?

  2 electrons
• What is the maximum number of electrons in the second shell?

  8 electrons
• What is the maximum number of electrons in the third shell?

  8 electrons