Describe the characteristics of a double replacement reaction, how it is identified, and types of compounds in the reactants and products. Give an example in your response.

its first and third is your answer i did the qustion the fourth isnt right

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8