Final answer:
Electrons are transferred from atoms of sodium to atoms of phosphorus. This transfer makes the sodium atoms positively charged and the phosphorus atoms negatively charged. As a result, the sodium and phosphorus atoms strongly attract each other.
Step-by-step explanation:
Sodium donates its outer electron becoming positively charged (Na+), whereas phosphorus gains electrons becoming negatively charged (P3-), resulting in an ionic bond due to the electrostatic attraction.
When sodium (Na) loses its one electron, it becomes a sodium ion (Na+) with a +1 charge. Similarly, phosphorus (P), which is more energy-efficient in gaining three electrons to fulfill its outer shell, becomes a phosphide ion (P3-) with a -3 charge. The ionic bond is formed due to the attraction between the positively charged sodium ions and the negatively charged phosphide ions, creating a stable compound.