Explain, in terms of sub-atomic particles, why the mass number of a magnesium atom is 24.

On the periodic table, Magnesium has the symbol 12Mg24, where 24 is the mass number and 12 is the atomic number. The atomic number is the number of protons found inside an atom, while the mass number tells us how many neutrons and protons are found in an atom. As the atomic number is 12, we can see we have 12 protons. To calculate the number of neutrons, we do 24-12, which gives us 12. Therefore, the mass number is 24 because Magnesium has 12 protons and 12 neutrons. 

Matthew N. A Level Maths tutor, GCSE Maths tutor, A Level Chemistry t...

7 months ago

Answered by Matthew, a GCSE Chemistry tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist


£30 /hr

Jacan C.

Degree: Theoretical Physics (Masters) - York University

Subjects offered: Chemistry, Science+ 3 more

Further Mathematics

“Hi, my name is Jacan. I am a Theoretical Physics third year at the University of York. I have had a real excitement for gaining an understanding in science at all levels through my education. This was, however, not always facilitated...”

£18 /hr

Laura B.

Degree: Chemistry (Bachelors) - York University

Subjects offered: Chemistry, Russian+ 2 more

-Personal Statements-

“Hello! My name is Laura and I am very passionate about science! I am currently studying Chemistry with Biological and Medicinal Chemistry at University of York and I really hope that my passion about science will inspire you!  I am ve...”

£18 /hr

Joel B.

Degree: Mathematics & Computer Science (Bachelors) - Manchester University

Subjects offered: Chemistry, Physics+ 3 more

Further Mathematics

“About Me: Hello, my name is Joel and I am currently a student at the University of Manchester studying for a joint honours in Mathematics & Computer Science. I have experience in teaching maths (and further maths) to students in the ag...”

MyTutor guarantee

About the author

Matthew N.

Currently unavailable: for new students

Degree: Chemistry (4 Years) [MChem] (Masters) - Manchester University

Subjects offered: Chemistry, Maths


“About Me:I'm a third year student at the University of Manchester studying for my masters degree in Chemistry. The main purpose of my tutorials, aside from allowing you to pass your exams with a great mark, is to get you interested i...”

MyTutor guarantee

You may also like...

Posts by Matthew

Explain how the electron pair repulsion theory can be used to deduce the shape of, and the bond angle in, NH3.

Explain, in terms of sub-atomic particles, why the mass number of a magnesium atom is 24.

Find the derivative of the following expression: y=x^3+2x^2+6x+5.

Rearrange the equation y=3x+2 to make x the subject.

Other GCSE Chemistry questions

What is an unsaturated hydrocarbon?

What is empirical formula and how is it worked out?

Aspirin C9H8O4 is made when salicylic acid C7H6O3 reacts with ethanoic anhydride C4H6O3 . The equation for this reaction is: C7H6O3 + C4H6O3 → C9H8O4 + CH3COOH Calculate the maximum mass of aspirin that could be made from 100 g of salicylic acid.

What is the mass (in grams) of 0.1 moles of CaCO3?

View GCSE Chemistry tutors


We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss