How to Draw Bohr-Rutherford Diagrams - Phosphorous

Summary

This video tutorial explains how to draw Bohr-Rutherford diagrams, using phosphorus (atomic number 15) as an example. The process involves identifying protons (15), neutrons (16), and electrons (15) for the element. It covers how to arrange electrons in shells: 2 in the first, 8 in the second, and 5 in the third shell. The video also highlights the concept of atomic mass and provides tips for accurately drawing the diagram. A note is included about the increasing complexity for elements beyond number 20, but the video focuses on atoms up to this point for simplicity.

Takeaways

• 😀 The first step in drawing a Bohr-Rutherford diagram is to determine the number of protons and neutrons in the atom.
• 😀 The number of protons is equal to the atomic number, which can be found on the periodic table.
• 😀 For phosphorus (P), the atomic number is 15, meaning it has 15 protons.
• 😀 The number of neutrons is calculated by subtracting the number of protons from the atomic mass. For phosphorus, this gives 16 neutrons.
• 😀 To draw the Bohr-Rutherford diagram, the nucleus (protons and neutrons) is represented by a small circle.
• 😀 Electrons are placed in concentric electron shells around the nucleus. The first shell can hold up to 2 electrons.
• 😀 The second electron shell can hold up to 8 electrons, and the third shell can hold up to 8 electrons as well.
• 😀 For phosphorus, after placing 2 electrons in the first shell and 8 in the second shell, there are 5 electrons left to place in the third shell.
• 😀 When drawing electrons in the shells, it's a convention to spread them out before pairing them up, but this may vary depending on the teacher's preference.
• 😀 The Bohr-Rutherford diagram for phosphorus should have 15 protons, 16 neutrons, and 15 electrons arranged in 3 shells: 2, 8, and 5 electrons respectively.
• 😀 For elements with atomic numbers greater than 20, the diagram becomes more complex, and you might not be asked to draw them in typical assignments.

Q & A

What is the first step in drawing a Bohr-Rutherford diagram?

The first step is to determine the number of protons and neutrons in the atom. The number of protons is the atomic number of the element, and the number of neutrons is calculated by subtracting the number of protons from the atomic weight.

How do you determine the number of neutrons in an atom?

The number of neutrons is found by subtracting the atomic number (number of protons) from the atomic weight (rounded to the nearest whole number) of the element.

In the case of phosphorus, how many protons and neutrons are there?

Phosphorus has 15 protons (since its atomic number is 15) and 16 neutrons (calculated by subtracting 15 protons from the atomic weight of 31).

What is the role of the electron shells in the Bohr-Rutherford diagram?

The electron shells are where electrons are placed around the nucleus. Electrons fill the shells starting from the innermost shell, and each shell can hold a specific number of electrons (2 in the first shell, 8 in the second and third shells).

How many electrons can be placed in each shell?

The first shell can hold up to 2 electrons, the second shell can hold up to 8 electrons, and the third shell can also hold up to 8 electrons, though fewer may be placed depending on the number of electrons in the atom.

How many electrons are in the Bohr-Rutherford diagram of phosphorus?

Phosphorus has 15 electrons, with 2 in the first shell, 8 in the second shell, and 5 in the third shell.

Why is it important to spread electrons around in the shells before pairing them?

Spreading the electrons around before pairing them follows a common convention in drawing Bohr-Rutherford diagrams, though it's not a strict rule. It is a way to represent the electron distribution more clearly.

Can the Bohr-Rutherford diagram for an atom go beyond 3 shells?

Yes, for elements with atomic numbers greater than 20, additional shells may be added to accommodate more electrons, though these cases are usually more complex and are not always required in basic diagrams.

What is the maximum number of electrons the third shell can hold?

The third shell can hold a maximum of 8 electrons, but for phosphorus, which has 15 electrons, only 5 electrons are placed in the third shell after filling the first two shells.

What should you do if you need to draw a Bohr-Rutherford diagram for an atom with more than 20 electrons?

For atoms with more than 20 electrons, you will need to add a fourth shell and continue placing electrons in the shells following the same rules, although the diagram becomes more complex as you move past the third shell.