Final answer:
An atom with 15 protons will also have 15 electrons to maintain electrical neutrality. The protons are located in the nucleus at the center of the atom. The number of protons determines the atomic number and the element, such as phosphorus with 15 protons and 15 electrons.
Step-by-step explanation:
If an atom has 15 protons, it must also have 15 electrons, because atoms are electrically neutral, with the number of negatively charged electrons balancing out the positively charged protons. In an atom, protons reside at the center, within a dense core known as the nucleus. The number of protons within an atom's nucleus is fundamental, as it defines the chemical element to which the atom belongs, a property referred to as the atomic number. Hydrogen, the simplest element, has one electron and one proton, whereas phosphorus, with an atomic number of 15, consists of fifteen electrons and fifteen protons.
The electrons are contained in energy levels or orbitals around the nucleus, and they follow a specific order of filling these orbitals. For example, the phosphorus atom fills its energy levels up to the 3p orbital, which will contain three out of its fifteen electrons.