Answer:
A- beryllium
B- calcium
C- magnesium
Explanation
NOTE: all element in group 2 have 2 balance electrons
First let’s start with B- number of electrons= number of protons which is equal to the atomic number. therefore, the answer is calcium as it’s atomic number is 20
C- magnesium will have three energy levels considering it has 12 electrons (2,8,2).
A- beryllium is the lightest one in group 2 as it has the atomic mass of 9.0122.
The true statement is :
B.The reaction will need an external energy source to proceed. It requires 150kJ more for it to take place. The difference between the energy consumed and the energy produced is 150kJ.
You change the independent variable in an experiment
