The atomic number of lead (Pb) is 82, and its mass number is 207.
How many protons, neutrons, and electrons does this neutral atom of lead (Pb) contain?
The Correct Answer and Explanation is :
The atomic number of lead (Pb) is 82, which indicates that a neutral atom of lead contains 82 protons. In a neutral atom, the number of electrons is equal to the number of protons to balance the positive charge of the protons. Therefore, a neutral atom of lead also has 82 electrons.
To find the number of neutrons in the atom, we use the mass number. The mass number is the sum of the number of protons and neutrons in the nucleus. For lead, the mass number is 207. The formula to determine the number of neutrons is:
[
\text{Number of neutrons} = \text{Mass number} – \text{Atomic number}
]
Substituting the known values:
[
\text{Number of neutrons} = 207 – 82 = 125
]
Thus, a neutral atom of lead contains:
- Protons: 82
- Neutrons: 125
- Electrons: 82
Explanation
- Atomic Number: The atomic number is a fundamental property of an element and determines its identity. It tells us how many protons are present in the nucleus of an atom. For lead, this number is 82, meaning lead is the 82nd element in the periodic table.
- Protons and Electrons: In a neutral atom, the positive charges of protons are exactly balanced by the negative charges of electrons. Hence, a neutral atom of lead, which has 82 protons, also has 82 electrons.
- Mass Number: The mass number gives us the total number of protons and neutrons in an atom’s nucleus. It is not a measure of the atom’s mass but rather a counting of these nucleons. The mass number of lead is 207, which includes both protons and neutrons.
- Calculating Neutrons: By subtracting the atomic number from the mass number, we can find the number of neutrons. In lead’s case, knowing the mass number (207) and the atomic number (82) allows us to determine that lead has 125 neutrons.
In summary, a neutral atom of lead contains 82 protons, 125 neutrons, and 82 electrons, contributing to its stability and unique chemical properties.