What is the atomic number of aluminium?

Analysis

The question asks for the atomic number of the element Aluminium (Al). The atomic number represents the number of protons found in the nucleus of an atom of that element.

Concept

In the Periodic Table of Elements, elements are arranged in increasing order of their atomic numbers. Aluminium is a metal found in Group 13 and Period 3. Its electronic configuration is $1s^2 2s^2 2p^6 3s^2 3p^1$. By summing the electrons (or counting the protons), we can determine its position.

Step-by-Step Solution

1. Recall the Periodic Table: Aluminium is the 13th element in the periodic table.
2. Verify the configuration: The total number of electrons in a neutral aluminium atom is $2 + 2 + 6 + 2 + 1 = 13$.
3. Relate to Atomic Number: Since the number of protons equals the number of electrons in a neutral atom, the atomic number is 13.
4. Evaluate the options: • A: 13 (Correct) • B: 26 (This is the approximate mass number of Aluminium, not the atomic number) • C: 14 (This is the atomic number of Silicon) • D: 12 (This is the atomic number of Magnesium)

Conclusion

The atomic number of Aluminium is 13.

Exam Tip

To remember the atomic numbers of the first 20 elements, use the mnemonic: Happy Henry Likes Beer But Could Not Obtain Food Near Nasty Moguls Always Sipping Potable Soda Clearly Arriving Kindly Calming. (H=1, He=2, Li=3, Be=4, B=5, C=6, N=7, O=8, F=9, Ne=10, Na=11, Mg=12, Al=13, Si=14, P=15, S=16, Cl=17, Ar=18, K=19, Ca=20).