Pure Substances are made of the same material throughout and have the same properties throughout. Pure substances cannot be separated into other substances. Some examples are carbon, iron, water, sugar, salt, nitrogen gas, and oxygen gas. Ur welcome.
Oxygen<span> is a </span>chemical element<span> having a symbol </span>O<span> and having an </span>atomic number<span> 8. Oxygen is a pure substance , and it is not a mixture or solution, Niether it is a compound ... Instead , it forms chemical compounds by reacting with other elements. So , according to above explanation , A. A pure substance , is the correct answer.</span>
Explanation: For an example, many scientists use scientific notation when referring to the sun and moon. They use the power of ten to refer to the large numbers of miles away from the earth.
Atomic number is protons + electrons Mass number is protons + neutrons So to calculate the number of neutrons, you do atomic number - atomic mass 31 - 84 = - 53