Introduction to Periodic Trends

The Periodic Table of Elements is not just a list of elements—it's a powerful tool that helps us understand how elements behave based on their position. One of the most important features of the periodic table is the presence of periodic trends.

Periodic trends are patterns in the properties of elements that repeat at regular intervals (or “periods”) across the table. These trends help scientists predict how elements will react, bond, and interact with other substances.

---

Major Periodic Trends

1. Atomic Radius

   • Definition: The distance from the nucleus to the outermost electron.

   • Trend:

     • Decreases across a period (left to right)

     • Increases down a group (top to bottom)

2. Ionization Energy

   • Definition: The energy required to remove an electron from an atom.

   • Trend:

     • Increases across a period

     • Decreases down a group

3. Electronegativity

   • Definition: An atom's ability to attract electrons in a chemical bond.

   • Trend:

     • Increases across a period

     • Decreases down a group

4. Electron Affinity

   • Definition: The energy change when an atom gains an electron.

   • Trend:

     • Generally increases across a period

     • Generally decreases down a group

---

Why Do These Trends Happen?

The trends occur mainly because of:

• The number of protons in the nucleus (affects pull on electrons)

• The distance between the nucleus and outer electrons

• The shielding effect (inner electrons blocking the pull from the nucleus)

---

Would you like a visual summary or a diagram to go with this?