Here’s a explanation of how elements are classified in the periodic table:
1. By Periods (Horizontal Rows)
- The table has 7 horizontal rows called periods.
- Elements in the same period have the same number of electron shells.
- Example:
- Period 2 → Li, Be, B, C, N, O, F, Ne (all have 2 electron shells)
2. By Groups (Vertical Columns)
- The table has 18 vertical columns called groups.
- Elements in the same group have the same number of valence electrons.
- Example:
- Group 1 → Li, Na, K (all have 1 valence electron)
3. By Type of Element
Elements are also classified as:
- Metals – shiny, malleable, conduct electricity (e.g., Fe, Cu)
- Nonmetals – dull, brittle, poor conductors (e.g., O, N, S)
- Metalloids – have properties of both metals and nonmetals (e.g., B, Si, As)
4. By Block (Electron Configuration)
Elements are sometimes grouped into blocks based on their outermost electrons:
- s-block: Groups 1–2 + H, He
- p-block: Groups 13–18
- d-block: Transition metals (Groups 3–12)
- f-block: Lanthanides and actinides
5. Special Groups
- Alkali metals: Group 1 (very reactive metals)
- Alkaline earth metals: Group 2
- Halogens: Group 17 (reactive nonmetals)
- Noble gases: Group 18 (inert gases)
In short:
- Horizontally: Periods (same number of shells)
- Vertically: Groups (same valence electrons)
- By type: Metals, nonmetals, metalloids
- By block: s, p, d, f