Video Transcript
The isotope oxygen-18 has the nuclide symbol 18 eight O. How many protons are there in atoms of oxygen-18?
Isotopes are atoms that have the same number of protons but a different number of neutrons. To distinguish between different isotopes, we can use nuclide notation. This is also called 𝐴 𝑍 𝐸 notation. In this notation, 𝐴 represents the mass number. The mass number is the sum of the number of protons and neutrons in the nucleus. 𝑍 represents the atomic number. When looking at a cell on the periodic table, the atomic number is frequently found above the element symbol. The atomic number also represents the number of protons in the nucleus. 𝐸 represents the chemical symbol of the element as found on the periodic table.
Looking at the nuclide symbol for oxygen-18, we can recognize that O is the chemical symbol of oxygen, 18 is the mass number, and eight is the atomic number. Since the atomic number is equal to the number of protons in the atom, atoms of oxygen-18 will have eight protons.
How many neutrons are there in atoms of oxygen-18?
We know that the mass number is equal to the number of protons plus the number of neutrons. We have also already established that the mass number is 18 and the number of protons is eight. We can substitute these into the equation and solve for the number of neutrons. Subtracting eight from both sides of the equation tells us that there are 10 neutrons in atoms of oxygen-18.
What is the mass number of oxygen-18?
In the nuclide symbol, the value in the top left is the mass number. The mass number is also written after the dash in hyphen notation. Thus, the mass number of oxygen-18 is 18.
