Question

How many protons, electrons and neutrons are there in 16g of $${}_8{O}^{16}$$?

Answer 1

Hint: The atom is denoted as $${}_Z{O}^A$$, where, A is the mass number of the atom and Z is the atomic number. Compare the given atom with $${}_Z{O}^A$$ to determine how many protons, neutrons and electrons are there in a single atom of $${}_Z{O}^A$$. Calculate the number of atoms in 16g of $${}_Z{O}^A$$ and therefore, calculate the number of protons, neutrons and electrons in 16g of $${}_Z{O}^A$$.

Complete step-by-step answer:
We know that the atom is denoted as $${}_Z{O}^A$$. Here, A is the mass number of the atom and Z is the atomic number. We know that the atomic number is the number of protons in the atom. We also know that the mass number is the sum of number of protons and number of neutrons.

Let us compare $${}_8{O}^{16}$$ with $${}_Z{O}^A$$. We get, the mass number of the oxygen atom is 16 and the atomic number of the oxygen is 8. Therefore, we can say there are 8 protons in the oxygen atom. We know that, in the atom, there are equal protons and electrons. Therefore, the number of electrons in the oxygen atom is also 8.

Since the mass number is the sum of number of protons and number neutrons, we have,
$$16=8+\text{number of neutrons}$$
$$\Rightarrow \text{Number of neutrons}=8$$

Therefore, in a single oxygen atom, there are 8 protons, 8 electrons and 8 neutrons.

Now, we have to calculate the number of atoms in the 16g of $${}_8{O}^{16}$$. We know that the number of moles of the gas is the ratio of the given mass of the substance to its molar mass or mass number. Therefore, we have,
$$\text{Number of moles}={\displaystyle \frac{16}{16}}$$
$$\Rightarrow \text{Number of moles}=1$$

We know that 1 mole of substance has a number of atoms equal to Avogadro’s number. Therefore, we have $$6.022\times {10}^{23}$$ number of atoms in 16g of $${}_8{O}^{16}$$.

Thus, the number of protons in the 16g of $${}_8{O}^{16}$$is,
$$8\times 6.022\times {10}^{23}=4.82\times {10}^{24}$$

The number of electrons in the 16g of $${}_8{O}^{16}$$ is,
$$8\times 6.022\times {10}^{23}=4.82\times {10}^{24}$$

And, the number of neutrons in the 16g of $${}_8{O}^{16}$$ is,
$$8\times 6.022\times {10}^{23}=4.82\times {10}^{24}$$

Note: Students must note that the oxygen is always found in nature in diatomic form. Therefore, there are 2 atoms for the single oxygen molecule. Thus, the count of protons, neutrons and electrons would be double. Also, the number of electrons is always equal to the number of protons in the atom but the number of neutrons in the atom is not always equal to the number of protons.