Uploaded August 2025 | Updated September 2026, 2 weeks ago
Overview of the Periodic Table
Dr. DeBacco
Dmitri Mendeleev- Created Periodic Table
Developed by Dmitri Mendeleev in 1869, who arranged elements by atomic mass and grouped them based on similar chemical properties, noticing recurring patterns ("periodicity").
He adjusted the atomic weights of some elements to better fit his table, improving the understanding of their chemical behavior.
This was used to predicted undiscovered elements and provided a basis for understanding periodic trends.
Elements
Each element is a pure substance made of atoms with the same number of protons (atomic number).
118 known elements exist, from hydrogen (atomic number 1) to oganesson (atomic number 118)
As of 2025
Elements are the building blocks of matter.
Atomic Number
Atomic Number: Elements are arranged by increasing atomic number (number of protons), which determines their identity.
This was established by Henry Moseley in 1913, refining Dmitri Mendeleev’s earlier table based on atomic weight.
Structure: Rows (Periods)
Rows (Periods): Seven horizontal rows, numbered 1 to 7, corresponding to the number of electron shells.
Each period reflects elements with increasing atomic numbers and changing properties.
Structure: Columns (Groups or Families)
Columns (Groups or Families): 18 vertical columns, grouping elements with similar chemical behaviors due to similar valence electron configurations.
For example:
Group 1: Alkali metals (Sodium (Na), highly reactive)
Group 18: Noble gases (Helium (He), inert)
Blocks
Blocks: The periodic table is divided into blocks based on the subshell (s, p, d, f) being filled by electrons:
s-block: Groups 1–2
Sodium (Na) and Calcium (Ca)
p-block: Groups 13–18
Carbon (C) and Oxygen (O)
d-block: Transition metals Groups 3–12
Iron (Fe) and Copper (Cu)
f-block: Lanthanides and actinides (below the main table)
Uranium (U)
Major Categories
Metals: Left side, conductive, malleable and can tarnish via chemical reactions.
Example: Iron (Fe) and Copper (Cu)
Nonmetals: Right side, poor conductors, varied states
Example: Oxygen (O2) as gas and Sulfur (S) as solid
Metalloids: Borderline elements with mixed properties
Example: Silicon (Si)
Actinides/Lanthanides: f-block elements, often radioactive, at the bottom.
Trends in Radius and Electronegativity
Atomic Radius: Decreases across a period (left to right) due to increasing nuclear charge; increases down a group as electron shells are added.
Electronegativity: Increases across a period, decreases down a group, affecting bonding and solubility.
Trends in Ionization Energy and Reactivity
Ionization Energy: Energy to remove an electron; increases across a period, decreases down a group.
Reactivity: Varies by group…
Group 1 metals are highly reactive
Group 18 gases are inert
The Periodic Table
How it Actually Looks…
Link to Lecture Slides: drive.google.com/file/d/1R45_dyfbubw2k-dublKKdQhQZWW6XqXa/view?usp=drive_link
*Due to the description character limit the full work cited for "Overview of the Periodic Table" can be viewed at... docs.google.com/document/d/17mnzrETeiBnne5FWJgPLrJdMGnfaVPq6/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
Overview of the Periodic Table
Dr. DeBacco
Dmitri Mendeleev- Created Periodic Table
Developed by Dmitri Mendeleev in 1869, who arranged elements by atomic mass and grouped them based on similar chemical properties, noticing recurring patterns ("periodicity").
He adjusted the atomic weights of some elements to better fit his table, improving the understanding of their chemical behavior.
This was used to predicted undiscovered elements and provided a basis for understanding periodic trends.
Elements
Each element is a pure substance made of atoms with the same number of protons (atomic number).
118 known elements exist, from hydrogen (atomic number 1) to oganesson (atomic number 118)
As of 2025
Elements are the building blocks of matter.
Atomic Number
Atomic Number: Elements are arranged by increasing atomic number (number of protons), which determines their identity.
This was established by Henry Moseley in 1913, refining Dmitri Mendeleev’s earlier table based on atomic weight.
Structure: Rows (Periods)
Rows (Periods): Seven horizontal rows, numbered 1 to 7, corresponding to the number of electron shells.
Each period reflects elements with increasing atomic numbers and changing properties.
Structure: Columns (Groups or Families)
Columns (Groups or Families): 18 vertical columns, grouping elements with similar chemical behaviors due to similar valence electron configurations.
For example:
Group 1: Alkali metals (Sodium (Na), highly reactive)
Group 18: Noble gases (Helium (He), inert)
Blocks
Blocks: The periodic table is divided into blocks based on the subshell (s, p, d, f) being filled by electrons:
s-block: Groups 1–2
Sodium (Na) and Calcium (Ca)
p-block: Groups 13–18
Carbon (C) and Oxygen (O)
d-block: Transition metals Groups 3–12
Iron (Fe) and Copper (Cu)
f-block: Lanthanides and actinides (below the main table)
Uranium (U)
Major Categories
Metals: Left side, conductive, malleable and can tarnish via chemical reactions.
Example: Iron (Fe) and Copper (Cu)
Nonmetals: Right side, poor conductors, varied states
Example: Oxygen (O2) as gas and Sulfur (S) as solid
Metalloids: Borderline elements with mixed properties
Example: Silicon (Si)
Actinides/Lanthanides: f-block elements, often radioactive, at the bottom.
Trends in Radius and Electronegativity
Atomic Radius: Decreases across a period (left to right) due to increasing nuclear charge; increases down a group as electron shells are added.
Electronegativity: Increases across a period, decreases down a group, affecting bonding and solubility.
Trends in Ionization Energy and Reactivity
Ionization Energy: Energy to remove an electron; increases across a period, decreases down a group.
Reactivity: Varies by group…
Group 1 metals are highly reactive
Group 18 gases are inert
The Periodic Table
How it Actually Looks…
Link to Lecture Slides: drive.google.com/file/d/1R45_dyfbubw2k-dublKKdQhQZWW6XqXa/view?usp=drive_link
*Due to the description character limit the full work cited for "Overview of the Periodic Table" can be viewed at... docs.google.com/document/d/17mnzrETeiBnne5FWJgPLrJdMGnfaVPq6/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
