Question

a. What information is given by the noble-gas notation \([{Ne}] 3 s^{2} ?\) b. What element does this represent?

Short answer

The notation \([{Ne}] 3s^{2}\) means the element has the electron configuration of neon plus 2 additional electrons in the 3s orbital, representing magnesium (Mg).

Step-by-step solution

Understand Noble-Gas Notation

Noble-gas notation is a shorthand electron configuration. It uses the symbol of the preceding noble gas in brackets followed by the electron configuration of the remaining electrons.

Identify the Noble Gas

The notation \([{Ne}]\) indicates that the element has all the electrons that neon (Ne) has. The electron configuration for neon is \(1s^{2} 2s^{2} 2p^{6}\), which totals 10 electrons.

Examine the Remaining Configuration

Following \([{Ne}]\), the notation gives \(3s^{2}\). This means there are 2 electrons in the 3s orbital.

Calculate the Total Number of Electrons

Add the number of electrons from neon (10) to the electrons in the 3s orbital (2). This gives a total of 12 electrons.

Determine the Element

The element with 12 electrons is magnesium, which is represented by the symbol Mg.

Key concepts

Electron Configuration

When we talk about electron configuration, we are referring to how electrons are distributed in an atom’s orbitals. Electrons occupy energy levels or shells around the nucleus. Each shell is labeled by a principal quantum number (n). For example, the first shell is n = 1, the second shell is n = 2, and so on. Within each shell, there are subshells (s, p, d, f) that contain orbitals where electrons are found.
Electrons fill the lowest energy levels first, according to the Aufbau principle. For instance, after the 1s orbital is filled, electrons move to the 2s orbital, then the 2p orbitals, and so on. Each orbital can hold a specific number of electrons: s orbitals can hold 2 electrons, p orbitals can hold 6, d orbitals can hold 10, and f orbitals can hold 14.
Writing the complete electron configuration for an element involves listing all the occupied orbitals in order. For instance, the electron configuration of neon (Ne) is written as 1s^2 2s^2 2p^6.

Noble Gases

Noble gases are found in Group 18 of the periodic table. These elements are known for being very stable because their outermost electron shell is full. This stability means they don't easily form compounds with other elements. Examples of noble gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).
Noble gas notation is a shorthand way of writing an element’s electron configuration. It uses the electron configuration of the nearest preceding noble gas to simplify the notation. For example, instead of writing out the full electron configuration for magnesium (Mg) as 1s^2 2s^2 2p^6 3s^2, we can use the noble gas notation, which is [{Ne}] 3s^2. Here, [{Ne}] represents all the electrons that neon (a noble gas) has, and 3s^2 represents the additional electrons in magnesium.

Magnesium

Magnesium (Mg) is an element with the atomic number 12. This means it has 12 protons in its nucleus and, in a neutral atom, it also has 12 electrons. Magnesium is in the second group of the periodic table and is classified as an alkaline earth metal.
The electron configuration of magnesium is 1s^2 2s^2 2p^6 3s^2. Using noble gas notation, it’s written as [{Ne}] 3s^2, which shows that magnesium has the same electron configuration as neon, plus two more electrons in the 3s orbital.
These two extra electrons give magnesium its chemical properties. When magnesium reacts, it typically loses these two electrons to form Mg^2+ ions. This gives it a stable electron configuration similar to that of neon, a noble gas.