Chemistry - Periodic Table

Periodic Trends

• Atomic Radius:
  • Decreases from left to right across a period due to increased nuclear charge and decreased shielding.
  • Increases down a group due to increased shielding and energy levels.
• Electronegativity:
  • Increases from left to right across a period due to increased nuclear charge and decreased shielding.
  • Decreases down a group due to increased shielding and energy levels.
• Ionization Energy:
  • Increases from left to right across a period due to increased nuclear charge and decreased shielding.
  • Decreases down a group due to increased shielding and energy levels.
• Electron Affinity:
  • Increases from left to right across a period due to increased nuclear charge and decreased shielding.
  • Decreases down a group due to increased shielding and energy levels.

Periodic Table History

• Early Development:
  • John Newlands (1863): Developed the Law of Octaves, which stated that elements exhibited similar properties at intervals of 8.
  • Julius Lothar Meyer (1864): Developed an early periodic table, but it was not widely accepted.
• Mendeleev's Contribution:
  • Dmitri Mendeleev (1869): Developed the modern periodic table, which organized elements by atomic weight and chemical properties.
  • Predicted the existence of undiscovered elements and left gaps in the table for them.

Element Classification

• Metals:
  • Typically shiny, malleable, and good conductors of electricity.
  • Found on the left side and center of the periodic table.
• Nonmetals:
  • Typically dull, brittle, and poor conductors of electricity.
  • Found on the right side of the periodic table.
• Metalloids:
  • Exhibits some properties of metals and some properties of nonmetals.
  • Found on the border between metals and nonmetals.

Atomic Structure

• Protons, Neutrons, and Electrons:
  • Protons: positively charged, found in the nucleus, and determine the element.
  • Neutrons: no charge, found in the nucleus, and contribute to the element's mass.
  • Electrons: negatively charged, found in energy levels, and determine the element's chemical properties.
• Energy Levels and Subshells:
  • Energy levels (n): the distance of an electron from the nucleus.
  • Subshells (l): the shape of the electron's orbit around the nucleus.
  • Orbitals: the specific path of an electron within a subshell.

Periodic Trends

• Atomic radius decreases from left to right across a period due to increased nuclear charge and decreased shielding.
• Atomic radius increases down a group due to increased shielding and energy levels.
• Electronegativity increases from left to right across a period due to increased nuclear charge and decreased shielding.
• Electronegativity decreases down a group due to increased shielding and energy levels.
• Ionization energy increases from left to right across a period due to increased nuclear charge and decreased shielding.
• Ionization energy decreases down a group due to increased shielding and energy levels.
• Electron affinity increases from left to right across a period due to increased nuclear charge and decreased shielding.
• Electron affinity decreases down a group due to increased shielding and energy levels.

Periodic Table History

• John Newlands developed the Law of Octaves in 1863, stating that elements exhibit similar properties at intervals of 8.
• Julius Lothar Meyer developed an early periodic table in 1864, but it was not widely accepted.
• Dmitri Mendeleev developed the modern periodic table in 1869, organizing elements by atomic weight and chemical properties.
• Mendeleev predicted the existence of undiscovered elements and left gaps in the table for them.

Element Classification

• Metals are typically shiny, malleable, and good conductors of electricity, found on the left side and center of the periodic table.
• Nonmetals are typically dull, brittle, and poor conductors of electricity, found on the right side of the periodic table.
• Metalloids exhibit some properties of metals and some properties of nonmetals, found on the border between metals and nonmetals.

Atomic Structure

• Protons are positively charged, found in the nucleus, and determine the element.
• Neutrons have no charge, are found in the nucleus, and contribute to the element's mass.
• Electrons are negatively charged, found in energy levels, and determine the element's chemical properties.
• Energy levels (n) refer to the distance of an electron from the nucleus.
• Subshells (l) refer to the shape of the electron's orbit around the nucleus.
• Orbitals refer to the specific path of an electron within a subshell.