Answer:

PROBLEM:

The following are elements except:

a.) carbon

b.) water

c.) magnesium

d.) water

ANSWER:

\large\underline{\boxed{\rm b)\:water\quad or\quad d)\:water}}

b)waterord)water

ELEMENTS

a pure substance that consists of only one type of atom; consisting only of atoms that all have the same numbers of protons in their atomic nuclei

example of which are Carbon (C) and Magnesium (Mg) in the problem; we have Nitrogen (N) as the most abundant gas element in the atmosphere

COMPOUND

it is formed by the chemical bonding of two or more elements; example of which is water, it is formed due to the chemical reaction between two atoms Hydrogen (H) and an Oxygen (O), the reason why we have \rm H_20H

2

0 as its chemical symbol

any substance composed of identical (the same) molecules consisting of atoms of two or more than two kinds of chemical elements