An atom of carbon has 6 protons. Its mass number is 12. How many neutrons are present in an atom of carbon?
6
Understanding Atomic Structure: Protons, Neutrons, and Mass Number
Atoms are the basic building blocks of matter. Each atom has a nucleus at its center, containing protons and neutrons. Electrons orbit the nucleus.
Let's define the key terms related to the question:
- Protons: Positively charged particles found in the nucleus. The number of protons determines the element and is called the atomic number ($\text{Z}$).
- Neutrons: Neutral particles found in the nucleus. They contribute to the mass of the atom but have no charge.
- Electrons: Negatively charged particles that orbit the nucleus. In a neutral atom, the number of electrons is equal to the number of protons.
- Mass Number: The total number of protons and neutrons in the nucleus of an atom. It is represented by the symbol $\text{A}$.
Relating Mass Number, Protons, and Neutrons
The mass number ($\text{A}$) of an atom is the sum of the number of protons ($\text{Z}$) and the number of neutrons ($\text{N}$). This relationship can be expressed by the formula:
\(\text{Mass Number (A) = Number of Protons (Z) + Number of Neutrons (N)}\)
To find the number of neutrons ($\text{N}$), we can rearrange this formula:
\(\text{Number of Neutrons (N) = Mass Number (A) - Number of Protons (Z)}\)
Calculating Neutrons in a Carbon Atom
The question provides information about a carbon atom:
- Number of protons = 6
- Mass number = 12
We know that the number of protons is also the atomic number ($\text{Z}$). So, for this carbon atom, $\text{Z} = 6$. The mass number ($\text{A}$) is given as 12.
Using the formula derived above, we can calculate the number of neutrons:
\(\text{N} = \text{A} - \text{Z}\)
Substitute the given values for the carbon atom:
\(\text{N} = 12 - 6\)
\(\text{N} = 6\)
Therefore, there are 6 neutrons present in this atom of carbon.
| Component | Number in this Carbon Atom |
|---|---|
| Protons ($\text{Z}$) | 6 |
| Mass Number ($\text{A}$) | 12 |
| Calculated Neutrons ($\text{N}$) | 6 |
Revision Table: Key Atomic Terms
| Term | Definition | Location in Atom |
|---|---|---|
| Proton | Positive charge, defines element (Atomic Number) | Nucleus |
| Neutron | No charge, contributes to mass | Nucleus |
| Electron | Negative charge, orbits nucleus | Outside nucleus (electron shells) |
| Atomic Number ($\text{Z}$) | Number of protons | Determined by nucleus |
| Mass Number ($\text{A}$) | Protons + Neutrons | Determined by nucleus |
Additional Information on Carbon Atoms and Isotopes
The question describes a common form of carbon, Carbon-12 ($\text{^{12}C}$). It has 6 protons and 6 neutrons (mass number 12). However, elements can exist as different isotopes.
Isotopes are atoms of the same element (same number of protons) but with different numbers of neutrons (and thus different mass numbers). Carbon also exists as Carbon-13 ($\text{^{13}C}$), which has 6 protons and 7 neutrons, and Carbon-14 ($\text{^{14}C}$), which has 6 protons and 8 neutrons. The number of protons (6) is what makes it carbon, regardless of the number of neutrons.
Important Questions from Structure of Atom
Identify the element having zero valency
The atomic number of an element is 8. How many electrons will it gain to form a compound with sodium?
What is the atomic number of nitrogen?
What are isobars?
Which of the following metals is the most reactive element?
