Question

Write the electron arrangement for each of the following atoms: (Example: sodium \(2,8,1\) ) a. phosphorus b. neon c. sulfur d. magnesium e. aluminum f. fluorine

Short answer

Phosphorus: 2,8,5; Neon: 2,8; Sulfur: 2,8,6; Magnesium: 2,8,2; Aluminum: 2,8,3; Fluorine: 2,7.

Step-by-step solution

Understand the exercise

This exercise involves writing the electron arrangement for each given atom. Each element's atomic number is needed from the periodic table.

Phosphorus

Phosphorus has an atomic number of 15. Distribute the 15 electrons in the order of filling: 2 in the first shell, 8 in the second shell, and the remaining 5 in the third shell. This gives the electron arrangement: Phosphorus: 2,8,5

Neon

Neon has an atomic number of 10. Distribute the 10 electrons: 2 in the first shell, and 8 in the second shell. This gives the electron arrangement: Neon: 2,8

Sulfur

Sulfur has an atomic number of 16. Distribute the 16 electrons: 2 in the first shell, 8 in the second shell, and the remaining 6 in the third shell. This gives the electron arrangement: Sulfur: 2,8,6

Magnesium

Magnesium has an atomic number of 12. Distribute the 12 electrons: 2 in the first shell, 8 in the second shell, and the remaining 2 in the third shell. This gives the electron arrangement: Magnesium: 2,8,2

Aluminum

Aluminum has an atomic number of 13. Distribute the 13 electrons: 2 in the first shell, 8 in the second shell, and the remaining 3 in the third shell. This gives the electron arrangement: Aluminum: 2,8,3

Fluorine

Fluorine has an atomic number of 9. Distribute the 9 electrons: 2 in the first shell, and 7 in the second shell. This gives the electron arrangement: Fluorine: 2,7

Key concepts

Atomic Number

The atomic number of an element tells us the number of protons in the nucleus of an atom. This is essential because the atomic number also indicates the number of electrons in a neutral atom.
Since electrons determine the electron arrangement, knowing the atomic number is the first step in writing the electron configuration.
For instance, the atomic number of sulfur is 16, meaning it has 16 protons and, when neutral, 16 electrons.
This information helps us to distribute electrons across different shells to find the electron arrangement.

• The atomic number is unique for each element and is listed in the periodic table.
• As you move from left to right in the periodic table, the atomic number increases by one.
• This incremental increase helps us understand the properties of elements and their electron configurations.

Periodic Table

The periodic table is an organized chart of elements, where elements are arranged in rows by increasing atomic number.
The table's structure allows us to predict the properties of elements, including their electron arrangement.
Understanding the periodic table is key to mastering electron configurations.

• The table is divided into rows called periods and columns known as groups.
• Elements in the same group have similar properties and electron configurations in their outer shell.
• The periodic table helps us quickly find the atomic number of elements, which is crucial for determining their electron arrangement.

For example, to find the electron arrangement for magnesium, we first note its atomic number (12) from the periodic table and then distribute the electrons accordingly.

Electron Shells

Electron shells are energy levels where electrons are arranged around the nucleus of an atom. Each shell can hold a certain number of electrons:

• The first shell can hold up to 2 electrons.
• The second shell can hold up to 8 electrons.
• The third shell can also hold 8 electrons initially but can expand to hold more in larger atoms.

When writing electron configurations, we fill the lowest energy levels (shells) first before moving to higher ones. This is why, for sulfur with an atomic number of 16, the distribution goes 2 electrons in the first shell, 8 in the second, and the remainder (6) in the third, resulting in an electron arrangement of 2,8,6.
By understanding and applying these rules, we can write the electron configurations for any element given its atomic number.