Answer:
No. of protons = 20
No. of electrons = 20
No. of neutrons = 20
Step-by-step explanation:
Part 1 :
Na, K and Rb are in the same group.
So, K and Rb are the two elements that have the same properties as sodium ( Na ).
Part 2 :
Atomic Number of Calcium = 20
Note :
Atomic Number = No. of protons
Therefore,
No. of protons = 20
Note :
No. of neutrons = No. of protons.
Therefore,
No. of neutrons = 20
Calcium is the 20th element, with 20 protons. Since a stable atom has a net charge of 0, it must have 20 electrons.
