The number of valence electrons in an atom depends on its position in the periodic table and the group number to which it belongs. Here's a breakdown of the number of valence electrons for elements in different groups:
Group 1 (Alkali Metals): 1 valence electron Group 2 (Alkaline Earth Metals): 2 valence electrons Group 13: 3 valence electrons Group 14: 4 valence electrons Group 15: 5 valence electrons Group 16: 6 valence electrons Group 17 (Halogens): 7 valence electrons Group 18 (Noble Gases): Full valence shell (typically 8 valence electrons, except helium with 2)
For example:
- Sodium (Na) is in Group 1 and has 1 valence electron.
- Carbon (C) is in Group 14 and has 4 valence electrons.
- Oxygen (O) is in Group 16 and has 6 valence electrons.
- Fluorine (F) is in Group 17 and has 7 valence electrons.
- Neon (Ne) is in Group 18 and has a full valence shell with 8 valence electrons.
It's important to note that the transition metals (Groups 3-12) have variable valence electrons, and their electron configurations can be more complex due to the involvement of d and f orbitals.