Question

Use the periodic table to write electron configurations for each element. (a) \(\mathrm{Al}\) (b) \(\mathrm{Be}\) (c) In (d) \(\mathrm{Zr}\)

Short answer

The electron configurations are: (a) Al: 1s^2 2s^2 2p^6 3s^2 3p^1, (b) Be: 1s^2 2s^2, (c) In: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^10 5p^1, (d) Zr: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^2.

Step-by-step solution

Locate Aluminum (Al) on the Periodic Table

Find Aluminum on the periodic table to determine its atomic number, which is 13. This gives us the total number of electrons to place in orbitals.

Write Electron Configuration for Al

Starting from Hydrogen, fill the orbitals in order of increasing energy until all 13 electrons are placed. The electron configuration for Al is thus: 1s^2 2s^2 2p^6 3s^2 3p^1.

Locate Beryllium (Be) on the Periodic Table

Find Beryllium on the periodic table to determine its atomic number, which is 4.

Write Electron Configuration for Be

Following the aufbau principle, the electron configuration for Be is: 1s^2 2s^2.

Locate Indium (In) on the Periodic Table

Find Indium on the periodic table to determine its atomic number, which is 49.

Write Electron Configuration for In

The electron configuration for In, following the pattern, will be: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^10 5p^1.

Locate Zirconium (Zr) on the Periodic Table

Determine the atomic number of Zirconium, which is 40. Hence, it has 40 electrons.

Write Electron Configuration for Zr

Applying the aufbau principle again, we get the electron configuration for Zr: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^2.

Key concepts

Aufbau Principle

Understanding the aufbau principle is fundamental for anyone delving into chemistry and its application in writing electron configurations. This principle, which translates to 'building up' in German, explains how electrons fill up atomic orbitals. Electrons are added sequentially to the lowest energy orbitals first before moving on to higher energy levels.

Imagine a hotel with a rule: 'Fill up all the ground floor rooms before opening up rooms on the higher floors.' This is similar to how the aufbau principle directs electron placement. The order of the 'rooms' or orbitals is determined by their energy levels, starting from 1s, then 2s, followed by 2p, and so on. This sequence follows the shape of a 'slanted z' or 'n' when viewed on a diagram commonly referred to as the 'aufbau diagram'.

However, there's a catch – the rule isn't outright linear due to electron-electron repulsions and the shapes of the orbitals. Consequently, an orbital such as 4s is filled before 3d, because 4s has a slightly lower energy. The aufbau principle sets the stage for two other key rules: Pauli's exclusion principle and Hund's rule, which dictate the specific ways electrons occupy available orbitals.

Periodic Table

The periodic table is not just a chart; it's a powerful tool for predicting chemical properties. Each of the 118 known elements occupies a unique position on the table, organized by increasing atomic number from left to right and top to bottom. The atomic number itself corresponds to the number of protons in the element's nucleus and, by extension, the number of electrons for a neutral atom.

The periodic table is divided into blocks that represent different orbital types – these include the 's', 'p', 'd', and 'f' blocks. The distribution of elements within these blocks reflects the order of orbital filling according to the aufbau principle. Elements in the same column, or group, share similar chemical properties due to their analogous outer electron configurations.

For students aiming to write electron configurations, the periodic table is pivotal. By observing the position of an element within the periodic table, one can deduce the outermost sublevel being filled with electrons and thus accurately 'construct' the element's electron configuration from the ground up, incrementally moving across the table.

Atomic Number

When learning about atomic structure, the atomic number is a term you'll encounter frequently. Signified as 'Z', the atomic number is the definitive fingerprint of an element, indicating the number of protons in an atom's nucleus. Since atoms are electrically neutral in their standard state, the number of protons is equal to the number of electrons.

The atomic number serves several pivotal roles in chemistry: it defines the element's position on the periodic table, infers its chemical behavior, and guides us in constructing electron configurations. For example, if an element has an atomic number of 15, it will have 15 protons and 15 electrons (assuming no ionization has occurred).

Why is this number important for electron configurations? Because knowing the total number of electrons in an atom allows us to use the aufbau principle effectively and arrange these electrons in the atom's orbitals. Starting with the atomic number, we scaffold an understanding of the atom's electron arrangement and can predict how it will interact with other elements in chemical reactions.