DERES At approximately what temperature does the
solubility of sodium chloride, NaCl, match the
solubility of potassium dichromate, K2Cr207?
30 °C
60 °C
50 °C
83 °C

Here's link to the

cutt.ly/rzNrBcz

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.

it's c. elements are placed in rows based on how may valencies electrons have.