Respuesta :
Part 1:
Calcium(Ca) And Strontium (Sr)
Part 2:
Protons: 19
Electrons: 19
(both are the same)
Neutrons:20
Subtract 19 From 39 And Get 20
If You Use This Pls Put it in your own words
Also Sorry if I'm late!
Answer:
Step-by-step explanation:
part 1: the elements that have the same properties as sodium are potassium and rubidium.
part 2: calcium has 20 protons, neutrons, and electrons.