He valence of selenium depends on which compound it is in. Selenium is very similar to sulfur. It may have a valence of 6; example selenium hexafluoride SeF6, selenium trioxide SeO3
<span>4; example selenium tetrafluoride SeF4, selenium dioxide SeO2 </span>
<span>2; example selenium difluoride SeF2, selenium dichloride SeCl2 </span>
<span>and -2; example hydrogen selenide H2Se</span>
Detects? i think so but don't quote me.
The number that never changes is the atomic mass (atomic number on the periodic table)
Answer:
139
Explanation:
i have to do it at my school