Calculating the Protons, Neutrons and Electrons for an Atom
Mr Barnes・2 minutes read
The mass number on the periodic table is the sum of protons and neutrons, while the atomic number indicates the number of protons and electrons in an atom, with the number of neutrons calculated by subtracting the atomic number from the mass number. Isotopes of an element have the same number of protons but different numbers of neutrons, requiring accurate calculations for each isotope to earn marks.
Insights
- The mass number on the periodic table combines protons and neutrons, while the atomic number signifies the protons and electrons in an atom. To find protons, neutrons, and electrons, subtract the atomic number from the mass number. For example, in an atom with a mass number of 7 and atomic number 3, there are 3 protons, 3 electrons, and 4 neutrons.
- Isotopes of an element share protons but differ in neutrons. In chlorine-37, there are 17 protons, 17 electrons, and 20 neutrons, while chlorine-35 has 17 protons, 17 electrons, and 18 neutrons. Correct calculations for each isotope yield 6 marks total.
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Recent questions
What does the mass number represent?
The sum of protons and neutrons in an atom.
How do you calculate the number of electrons in an atom?
Subtract the atomic number from the mass number.
What is the significance of isotopes in chemistry?
Isotopes have the same number of protons but different numbers of neutrons.
How do you calculate the number of neutrons in an atom?
Subtract the atomic number from the mass number.
Why is it important to understand the structure of an atom?
Understanding the structure helps predict an element's properties.
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Summary
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Understanding Atomic Structure and Isotopes
- The mass number on the periodic table represents the sum of protons and neutrons, while the atomic number indicates the number of protons and electrons in an atom. To determine the number of protons, neutrons, and electrons in an atom, subtract the atomic number from the mass number. For example, in an atom with a mass number of 7 and an atomic number of 3, there are 3 protons, 3 electrons, and 4 neutrons.
- When calculating the number of protons, neutrons, and electrons for different isotopes of an element like chlorine, remember that isotopes have the same number of protons but different numbers of neutrons. For instance, in chlorine-37, there are 17 protons, 17 electrons, and 20 neutrons, while in chlorine-35, there are 17 protons, 17 electrons, and 18 neutrons. Each correct calculation earns a mark, with a total of 6 marks for both isotopes.
