Which element in the modern periodic table has the electronic configuration 2, 8, 3 in its neutral atom?

Introduction / Context:
Electronic configuration describes how electrons are distributed among the shells or energy levels of an atom. For lighter elements, school level chemistry often uses a simple notation such as 2, 8, 3 to represent electrons in the first, second and third shells. Recognising which element corresponds to a given configuration is important for understanding periodic trends, valency and chemical behaviour. This question asks you to identify the element whose neutral atom has the configuration 2, 8, 3.

Given Data / Assumptions:

• The configuration 2, 8, 3 means 2 electrons in the first shell, 8 in the second and 3 in the third shell.
• The total number of electrons in a neutral atom equals its atomic number.
• The options include magnesium, sodium, aluminium, argon and neon.
• We assume the simple shell model often used up to calcium in school chemistry.

Concept / Approach:
To identify the element, we add the electrons in all shells in the configuration. The sum gives the atomic number, which can then be matched to the correct element name. The configuration 2, 8, 3 sums to 13, so we look for the element with atomic number 13, which is aluminium. Magnesium has atomic number 12, sodium has 11, neon has 10 and argon has 18. This straightforward calculation connects shell configuration with the periodic table entry.

Step-by-Step Solution:
Step 1: Add the electrons indicated in the configuration 2, 8, 3: 2 plus 8 plus 3 equals 13. Step 2: The total number of electrons in a neutral atom is equal to its atomic number. Step 3: Therefore, the atomic number corresponding to this configuration is 13. Step 4: Recall that the element with atomic number 13 in the modern periodic table is aluminium (symbol Al). Step 5: Check the other options: sodium has atomic number 11 with configuration 2, 8, 1; magnesium has 12 with configuration 2, 8, 2; argon has 18 with configuration 2, 8, 8; neon has 10 with configuration 2, 8. Step 6: None of the other elements match a total of 13 electrons, confirming aluminium as the correct choice.

Verification / Alternative check:
Using the periodic table, you can count positions from hydrogen upwards to confirm that aluminium is element 13. Aluminium is located in period 3 and group 13, which is consistent with an outer shell containing three electrons. Its valency is often three in compounds such as aluminium oxide and aluminium chloride, matching the three valence electrons implied by the configuration 2, 8, 3. These independent checks from periodic position and common valencies confirm that aluminium is the element with the given configuration.

Why Other Options Are Wrong:
Option A, magnesium, has atomic number 12 and configuration 2, 8, 2, with only two valence electrons. Option B, sodium, has atomic number 11 and configuration 2, 8, 1, with one valence electron. Option D, argon, is a noble gas with atomic number 18 and configuration 2, 8, 8, with a completely filled outer shell. Option E, neon, has atomic number 10 and configuration 2, 8, also with a filled outer shell. None of these match the specified configuration 2, 8, 3. Only option C, aluminium with atomic number 13, fits correctly.

Common Pitfalls:
Students sometimes make arithmetic mistakes when adding the electrons in each shell or they may misremember atomic numbers. Another common error is to think of magnesium when they see a configuration ending in 2 or to match argon incorrectly because it is also in period 3. To avoid these problems, always first sum the electron counts to get the atomic number, and then cross check this number with a periodic table or your memorised list of elements up to at least 20. This systematic approach reduces confusion and ensures accuracy.

Final Answer:
The element with electronic configuration 2, 8, 3 is Aluminium (atomic number 13), which has three valence electrons in its outermost shell.