To determine the number of valence electrons in bromine (Br) and draw the Lewis dot structure for bromine gas (Br₂), we can follow a systematic approach.
Step 1: Find the number of valence electrons.
Bromine is located in Group 17 (or VIIA) of the periodic table. Elements in this group have seven valence electrons. As Br₂ consists of two bromine atoms, we calculate the total number of valence electrons as follows:
Valence electrons in Br₂ = 2 (Br atoms) × 7 (valence electrons per Br) = 14 valence electrons.
Step 2: Draw the Lewis dot structure.
In the Lewis dot structure, each valence electron is represented as a dot. To depict the Br₂ molecule:
- Start with two Br atoms next to each other.
- Each Br atom will have 7 dots representing its 7 valence electrons: 6 dots are arranged around the Br atoms to show bonding and lone pairs, while 1 dot is reserved for forming a bond.
- Br₂ will share one pair of electrons (1 bond), which means we can draw a line (representing a single bond) between the two Br atoms.
The final Lewis dot structure would appear as follows:
:Br:—:Br: : :
This structure confirms that Br₂ is a diatomic molecule held together by a single bond. Each bromine atom shares one pair of electrons, satisfying the octet rule, since each atom effectively has access to 8 electrons.
In summary, Br₂ has 14 valence electrons, and its Lewis dot structure reflects the shared bond and the remaining lone pairs on each bromine atom.