Periodicity

• What is the periodic table?

  An organized list of all known elements
• How is the periodic table arranged?

  By increasing atomic number from 1 to 118
• What does the structure of the periodic table reveal?

  Patterns that help understand element properties
• What are the rows in the periodic table called?

  Periods
• How are elements arranged in periods?

  Based on the number of electron shells
• How many shells do elements in the first row have?

  One shell
• How many shells do elements in the second row have?

  Two shells
• What does the period number correspond to?

  The number of electron shells
• What are the columns in the periodic table called?

  Groups
• Why are elements aligned vertically in groups?

  If they have similar outer-shell configurations
• What do similar outer-shell configurations indicate?

  Similar chemical properties among elements
• What are outer electrons called?

  Valence electrons
• What determines an element's chemical reactivity?

  The outer electrons, or valence electrons
• Who proposed the first working model of the periodic table?

  Dmitri Mendeleev
• In what year was the first periodic table proposed?

  1869
• Where is carbon found in the periodic table?

  Group 4 and Period 2
• How many valence electrons does carbon have?

  Four valence electrons
• What does carbon's valence electron configuration indicate?

  Similar chemical properties to Group 4 elements
• What are the four main blocks of the periodic table?

  • s-block: Groups 1 and 2
  • p-block: Groups 3 to 8
  • d-block: Transition metals
  • f-block: Lanthanides and actinides
• What elements are in the s-block?

  Groups 1 and 2, including H and He
• What is the outer shell configuration of s-block elements?

  Only s-electrons
• What are the key traits of s-block elements?

  Highly reactive metals with similar properties
• What elements are in the p-block?

  Groups 3 to 8
• What is the outer shell configuration of p-block elements?

  At least one p-electron
• What are the key traits of p-block elements?

  Includes metals, metalloids, and nonmetals
• What elements are in the d-block?

  Transition metals
• What is the outer shell configuration of d-block elements?

  At least one d-electron and one s-electron
• What are the key traits of d-block elements?

  Known for forming coloured compounds
• What elements are in the f-block?

  Lanthanides and actinides
• What is the outer shell configuration of f-block elements?

  At least one f-electron and one s-electron
• What are the key traits of f-block elements?

  Known for complex electron configurations
• What do periodic trends reveal?

  Clear patterns in physical and chemical properties
• Why do elements in the same group have similar properties?

  They have the same number of valence electrons
• What happens to properties as you move across a period?

  They change gradually due to atomic structure
• What is the trend in reactivity for alkali metals?

  They are highly reactive and soft
• What happens to atomic radius across a period?

  It decreases from left to right
• How is atomic radius defined?

  Distance from nucleus to outermost shell
• What causes the decrease in atomic radius across a period?

  Increased positive charge pulls electrons closer
• What remains constant across a period despite increasing nuclear charge?

  The number of inner electron shells
• What is the atomic radius of chlorine?

  99 pm