Problem 67 - Chemistry Matter and Change

Question

Carbon A carbon atom has a mass number of 12 and an atomic number of \(6 .\) How many neutrons does it have?

Step-by-Step Solution

Answer

Carbon has 6 neutrons.

Step 1: Understanding Atomic Number

The atomic number of an element is the number of protons in the nucleus of an atom. For carbon, the atomic number is 6, meaning there are 6 protons.

Step 2: Defining Mass Number

The mass number of an element is the sum of the number of protons and neutrons in the nucleus. For carbon, the mass number is 12.

Step 3: Calculating Neutrons

To find the number of neutrons, subtract the atomic number from the mass number. The formula is: \( \text{Number of neutrons} = \text{Mass number} - \text{Atomic number} \).

Step 4: Applying the Formula

Substitute the known values into the formula: \( \text{Number of neutrons} = 12 - 6 \), which equals 6.

Key Concepts

Atomic Number

The atomic number of an element is fundamental to its identity on the periodic table. It tells us how many protons are in the nucleus of an atom of the element.
In simpler terms, the atomic number directly correlates to the number of protons, which are positively charged particles inside an atom's nucleus.
It's important to remember that, normally, the number of protons equals the number of electrons surrounding the nucleus, which helps balance the positive charge.

• The atomic number is denoted by the symbol 'Z' in scientific notation.
• For carbon, the atomic number is 6.
• This number also defines the element's position on the periodic table.

The atomic number is key to understanding not only the structure but also the chemical properties of an element. Because protons make up the charge and identity of an atom, knowing the atomic number helps predict how atoms will interact in a chemical reaction.

Mass Number

The mass number is another crucial concept in atomic structure. It represents the total count of two types of particles found in the nucleus: protons and neutrons.
Unlike the atomic number, the mass number isn't listed on the periodic table because it can vary for different isotopes of an element. To understand mass number better:

• The mass number is denoted by the symbol 'A'.
• It equals the sum of protons and neutrons in an atom's nucleus.
• For carbon, the commonly referred mass number is 12.

This number gives us an idea of the isotope of the element we are dealing with, which is essential in various scientific applications, such as radiometric dating and nuclear physics. Each isotope of an element has the same number of protons but a different number of neutrons, thus a different mass number.
Remember, the mass number is a whole number and isn't the same as the atomic mass, which is measured in atomic mass units and typically includes decimals.

Neutrons

Neutrons are neutral particles within the nucleus and are key to understanding isotope differences and stability of atoms.
Unlike protons and electrons, neutrons do not have any charge, which is why they are termed 'neutral.' However, they add to the mass of an atom. To find their count in an atom, you can utilize the relationship between atomic and mass numbers. Here's how you can calculate the number of neutrons:

• Use the formula: \[ \text{Number of neutrons} = \text{Mass number} - \text{Atomic number} \]
• For carbon with a mass number of 12 and atomic number of 6, the calculation is simple: 12 - 6 = 6 neutrons.

Neutrons are crucial for the stability of an atom. They help glue protons together in the nucleus, offsetting the electromagnetic repulsion between similarly charged protons.
In summary, while neutrons might seem unassuming compared to positively charged protons or negatively charged electrons, they play an essential role in the chemical behavior and stability of elements.