What does the number 18.9984 represent in the image?
a) the atomic number of fluorine
b) the number of protons in fluorine
c) the number of electrons in fluorine
d) the average atomic mass of fluorine

The element symbol in chemistry comprises atomic number and mass number.

Atomic number is written on the top of element and mass number is written at the bottom.

For eg:

If Y is an element that is having atomic number a and mass number x. Then its denotion will be:

ᵃYₓ.

So here ⁹F₁₈.₉₉

Here 18.99 will denote mass number while 9 will denote atomic number.

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