Final Answer:
In electron configuration symbols, an up arrow (↑) represents the spin of an electron, indicating a positive 1/2 spin according to the Pauli Exclusion Principle.
Step-by-step explanation:
In electron configuration symbols, an up arrow (↑) indicates the spin of an electron. The arrow is used to represent the intrinsic angular momentum or "spin" of an electron. According to the Pauli Exclusion Principle, no two electrons in an atom can have the same set of four quantum numbers, and this includes the spin quantum number.
The spin of an electron can have two possible values: +1/2 or -1/2. The up arrow represents a positive 1/2 spin. When writing electron configurations, up arrows are often used in conjunction with down arrows (↓), which represents a negative 1/2 spin, to depict the pairing of electrons in an orbital.
For example, in the electron configuration for helium (He), which has two electrons in its 1s orbital, the notation would be 1s² with one up arrow and one down arrow to represent the opposite spins of the two electrons in the orbital.