The atomic number of lead is 82. Its mass number is 207. How many protons, neutrons, and electrons does the atom of lead contain?
The correct answer and explanation is:
To determine the number of protons, neutrons, and electrons in a lead atom, we need to use the information provided:
- Protons: The atomic number of an element indicates the number of protons in the nucleus of an atom. Since the atomic number of lead (Pb) is 82, the number of protons is 82.
- Electrons: In a neutral atom, the number of electrons equals the number of protons. Therefore, in a neutral lead atom, the number of electrons is also 82.
- Neutrons: The mass number of an atom is the sum of protons and neutrons in its nucleus. The mass number of lead is 207, and since there are 82 protons, the number of neutrons can be found by subtracting the number of protons from the mass number: Neutrons=Mass number−Protons=207−82=125\text{Neutrons} = \text{Mass number} – \text{Protons} = 207 – 82 = 125
Thus, the atom of lead contains:
- 82 protons
- 125 neutrons
- 82 electrons (if the atom is neutral)
The protons are positively charged and located in the nucleus of the atom. The electrons are negatively charged and orbit the nucleus in various energy levels or shells. The neutrons are neutral particles also located in the nucleus, and they help stabilize the nucleus by balancing the repulsive forces between the positively charged protons.
This structure is key to understanding the behavior of lead in chemical reactions and its properties in the periodic table.