Lesson 2: Electronic Configuration using Standard Written Notation

Electron Configuration (No.1)

uses the symbols of the orbitals and the number of electrons (written as supercripts) that occupy the orbital

What is electronic configuration?

A description of where electrons are in a molecule or atom, showing how electrons occupy orbitals with characteristic energy levels.

How does the number of electrons in a system affect the energy levels used?

Systems with more electrons occupy more energy levels and utilize higher energy levels.

What are two ways electron configurations can be represented?

By standard written notation or by orbital diagrams.

When did the notation for electron distribution in atomic orbitals come into practice?

Shortly after the Bohr model of the atom was presented by Ernest Rutherford and Niels Bohr in 1913

What does the term "Aufbau" in Aufbau principle mean?

“Build up” (from the German word Aufbeen).

What does the Aufbau principle state?

Electrons occupy orbitals of lower energy first before filling higher energy orbitals.

On what is the filling order of orbitals in the Aufbau principle based?

On the principal energy levels and sublevels.

How are principal energy levels assigned, and what do they indicate?

Assigned values from n = 1 to 7, indicating increasing energy as they are farther from the nucleus

Writing the elctron Configuration Shorthand Method (Condensed Form)

The shorthand methos uses the group 18 elements, the noble gases as a bookmark.

How is the periodic table helpful in writing electron configurations?

It indicates the principal energy levels and sublevels, showing how electrons are arranged in atoms.

What does the principal energy level correspond to on the periodic table?

An integer (1–7) that matches the periods (rows) of the periodic table.

What does each successive integer of the principal energy level represent?

A generally higher energy level than the previous one.

What letters indicate the sublevels in electron configurations?

s, p, d, and f.

How are groups or blocks of the periodic table related to sublevels?

They share the same sublevel and are divided into blocks (s-block, p-block, d-block, f-block).

n what type of elements do exceptions to the Aufbau principle usually occur?

In the d-block elements

Why do some d-block elements deviate from the Aufbau principle?

Because half-filled and fully filled sublevels are more stable than partially filled ones.

What arrangement increases the stability of atoms in anomalous configurations?

Half-filled or completely filled sublevels.

What does minimizing electron–electron repulsion do in anomalous configurations?

It adds stability to the atom.

Where can d-block elements (which show Aufbau exceptions) be found?

In the d-block of the periodic table (transition metals).

For the d-block elements

Half-filled and completely filled sublevels are more stable than the partially filled ones. Arrangement like this, indicates that repulsion (electrostatic repulsion between electrons is minimized adding stability of atoms.

What is the shorthand (condensed) method of writing electron configurations?

A method that uses noble gases (Group 18 elements) as bookmarks to shorten electron configurations.

Which elements are used as bookmarks in the shorthand method?

Noble gases (Group 18 elements).

How is a noble gas represented in shorthand notation?

Placed in brackets, e.g., [Ar], [Ne].

In shorthand notation, what noble gas is used for bromine?

Argon (Ar).

What is the shorthand electron configuration of bromine?

[Ar] 4s² 3d¹⁰ 4p⁵.

n shorthand notation, what noble gas is used for chlorine?

Neon (Ne).

Only the representative elements beyond the first noble gas in each period (basically all elements after a noble gas)

can use the condensed (shorthand) electron configuration.

What does the sum of the superscripts in an electron configuration represent?

The total number of electrons in the atom, equal to the number of protons (atomic number).

How many electrons does a neutral calcium atom have?

20 electrons.

What is the electron configuration of neutral calcium (Ca, Z = 20)?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s².

What happens to the electron configuration when calcium forms a Ca²⁺ ion?

It loses 2 electrons, giving a total of 18 electrons.

What is the electron configuration of Ca²⁺?

[1s² 2s² 2p⁶ 3s² 3p⁶]²⁺

What does the "+2" in Ca²⁺ indicate in terms of electrons and protons?

The atom has 20 protons but only 18 electrons (2 fewer electrons than protons).

How many electrons does neutral oxygen have?

8 electrons.

What happens to the electron configuration when oxygen forms O²⁻?

It gains 2 electrons, giving a total of 10 electrons.

What is the electron configuration of O²⁻?

[1s² 2s² 2p⁶]²⁻

What does the “–2” in O²⁻ indicate in terms of electrons and protons?

The atom has 8 protons but 10 electrons (2 more electrons than protons).

Valence Configuration

The electronic configuration representing the outermost subshells

Valence Electrons

The number of electrons in the outermost subshells.