Question

I
three at a time and arranged in die as
the atomic weight of the middle element is the average of the alotnie
weights of the first and third elements. This statement is called the
Dobereiner's law of triads.
Activity 1
Observe the following table.
Elements in each row represent a triad.
Group Elements and their Atomic weight
3rd elements Atomic
Potassium (K)
39.0
7.0 + 39.0
= 23.0
2
B
Barium (Ba)
1370
400+1310 = 88
С
Lithium(Li) Sodium (Na)
7.0
23.0
Calcium (Ca) Strontium(sr)
40.0
87.5
Chlorine (CD) Bromine (Br)
35.5
80.0
Sulphur (S) Selenium (Se)
32.0
78.0
Manganese(Mn) Chromium(Cr)
55.0
52.0
35.5 +1270
lodine (1)
127.0
Tellurium (Te) 390 4125
125.0
Iron (Fe)
56.0
E
55.0+ 5.0-55.5
128
Class
Classification of Elements - The Periodic Table
Arithmetic mean of 3 Rd elements Atomic weight​

Answer 1

Answer:

The answer is Magnesium(Mn)Chromium(Cr)