Sure, let’s determine which of these elements has two valence electrons.
1. Hydrogen (H) - Hydrogen is an element with one electron and one proton. Being positioned in Group 1 of the periodic table, it has one valence electron.
2. Barium (Ba) - Barium is an alkaline earth metal, positioned in Group 2 of the periodic table. The elements in this group have two valence electrons.
3. Nitrogen (N) - Nitrogen belongs to Group 15 (formerly known as Group 5A). It has a total of five valence electrons.
4. Krypton (Kr) - Krypton is a noble gas located in Group 18 (formerly Group 8A). Noble gases are characterized by having full valence shells, which in the case of krypton, it means having eight valence electrons.
5. Bromine (Br) - Bromine is a halogen in Group 17 (formerly Group 7A). It has seven valence electrons.
Based on this analysis, the element that has two valence electrons is barium (Ba).
So, the correct answer is:
O B. barium (Ba)
