Answer:
- An iodine atom has 7 valence electrons.
Step-by-step explanation:
Iodine is a halogen so it is the group (column number) 17 of the periodic table. It is a representative element.
The number of valence electrons for the representative elements is equal to the second digit of the group number. So, group 17 means that iodince has 7 valence electrons.
Now, more formally, the valence electrons are the electrons in the outermost shell of the atom and you can determine how many of them an atom has by doing the electron configuration.
These are the steps:
- Atomic number, of iodine, Z = 53
- Number of electrons of the neutral atom = number of protons = 53
- Distribute the electrons in ascending order of orbital energies, following Aufbau's rules:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵
- If you count the electrons you must obtain 53: 2 + 2 +6 + 2 + 6 + 2 + 10 + 6 + 2 + 10 + 5 = 53.
- The valence electrons are those in the highest principal energy level: 5s² 5p⁵, i.e 2 + 5 = 7.