Which of the following are true for an element?       (i)Atomic number= number of protons + number of electrons      (ii)Mass number = number of protons+ number of neutrons      (iii)Atomic mass= number of protons= number of neutrons      (iv)Atomic number = number of protons = number of electrons​

ii and iv

Explanation:

atomic mass is the sum of protons and neutrons

protons ( postively charged) usually have the same number like electrons( negatively charged)

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e