# What is the neutron:proton ratio for the nucleus "_82^206Pb?

Dec 14, 2016

The answer is 124 neutrons to 82 protons (very close of a 3:2 ratio)

#### Explanation:

The 206 seen in the upper left of the symbol is the mass number of the isotope and tells us the total number of nucleons (neutrons and protons combined) in the nucleus. The number at lower left is the atomic number, and gives the number of protons only. So, a quick subtraction 206 - 82 tells us that 124 particles in the nucleus must be neutrons!

Dec 14, 2016

The neutron to proton ratio in the nucleus of the isotope lead-206 is 62:41.

#### Explanation:

We first need to determine the number of protons and neutrons that are present in the nucleus of the isotope lead-206.

The nuclear notation $\text{_82^206"Pb}$ gives us the mass number, 206, for this isotope of lead, and the atomic number of lead, 82.

The atomic number of any isotope of any element is the number of protons in its atomic nucleus. So any atom of lead-206 has $82$ protons. However, different isotopes have different numbers of neutrons.

The mass number of an isotope of any element is the sum of the protons and neutrons in the atomic nucleus. The mass number for this isotope of lead is 206. We can determine the number of neutrons by subtracting the number of protons, $82$, from the mass number, $206$.

$206 - 82 = 124$

The nucleus of a lead-206 isotope has 82 protons and 124 neutrons.

The neutron:proton ratio is "124:82, which can be reduces to $62 : 41$.