Explain how Mendeleev was able to predict the properties of undiscovered elements. Check all possible answers.

He was able to predict the properties because he left gaps for undiscovered elements

Explanation:

Mendeleev discovered there was undiscovered elements and grouped them similarly and periodically

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6