Question

(a) What are "valence electrons"? (b) What are "core electrons"? (c) What does each box in an orbital diagram represent? (d) What object is represented by the half arrows in an orbital diagram? What does the direction of the arrow signify?

Short answer

(a) Valence electrons are the electrons found in an atom's outermost electron shell, playing a crucial role in chemical reactions and bonding. (b) Core electrons are the electrons found in the inner electron shells of an atom, essential for maintaining atom stability and shielding the nucleus from valence electrons. (c) Each box in an orbital diagram represents an individual orbital within an electron shell, where orbitals are regions of space within an atom where electrons are most likely to be found. (d) Half arrows within a box of an orbital diagram represent an electron, and their direction indicates the electron's spin state: up for positive (+1/2) spin and down for negative (-1/2) spin.

Step-by-step solution

(a) Definition of Valence Electrons

Valence electrons are the electrons found in an atom's outermost electron shell. They play a crucial role in chemical reactions and bonding, as they are the electrons that are available for sharing, gaining, or losing during these processes. Valence electrons determine the reactivity and chemistry of an element.

(b) Definition of Core Electrons

Core electrons are the electrons found in the inner electron shells of an atom. These electrons are not involved in chemical reactions, as they are more tightly bound to the nucleus and lie closer to it. Core electrons are essential for maintaining the stability of an atom and shielding the positively charged nucleus from the valence electrons.

(c) Orbital Diagram Box Representation

Each box in an orbital diagram represents an individual orbital within an electron shell. Orbitals are simply regions of space within an atom where electrons are most likely to be found. In the diagram, each orbital can contain a maximum of two electrons, following the Pauli Exclusion Principle.

(d) Half Arrows in Orbital Diagram and Arrow Direction

The half arrows within a box of an orbital diagram represent an electron present in that orbital. The direction of the arrow, either up or down, signifies the electron's spin state: an up arrow indicates a positive or +1/2 spin, while a down arrow indicates a negative or -1/2 spin. The Pauli Exclusion Principle states that two electrons in the same orbital must have opposite spins, so when two electrons are present in a single box, one arrow will point upwards and the other will point downwards.