Groups and Electronic Configuration

Elements in the same group have the same number of valence electrons.

• Example: Group 1 (Alkali Metals): All elements have one valence electron.
• Example: Group 2 (Alkaline Earth Metals): Beryllium (Be), Magnesium (Mg), and Calcium (Ca) all have two valence electrons.
• Example: Group 17 (Halogens): Fluorine (F) and Chlorine (Cl) have seven valence electrons.

Going down a group, one electronic shell is added for each successive element, but the valence electron configuration remains the same.

• Elements are arranged in increasing atomic number order.
• 18 vertical columns (groups): Elements in the same group share similar chemical properties with a gradual variation down the group.
• 7 horizontal rows (periods): Properties gradually change from left to right across a period.

Elements Beyond Uranium:

• Uranium (atomic number 92) is the last naturally occurring element.
• Elements beyond uranium (atomic numbers 93-118) are artificially created and are radioactive and unstable with a short lifespan.

Thus, the electronic configuration plays a fundamental role in determining the group and period placement of elements, influencing their chemical properties and periodic trends.