As per the question we have been given the element platinum.we are asked to calculate the number of protons and electrons of the neutral atom just before platinum in the periodic table.
A neutral atom is that atom which has no charge. It is so as it contains same number of protons and neutrons.
Before going get our solution first we have to know something about the atomic number of an element.The atomic number of an element is defined as the number of protons present inside the nucleus or the number of electrons present in a stable isolated atom which is neutral in nature.
Hence atomic number Z= Number of protons= number of electrons in an neutral atom.
we know that platinum is present in 6th period of the modern periodic table.The atomic number of platinum is 78.Hence the element which comes just before platinum and neutral is Iridium. It has an atomic number of 77.
Hence the number protons present inside it's nucleus is 77.
A neutral atom of Iridium must contain 77 number of electrons.
Hence a neutral atom of the element which comes just before platinum has 77 protons and 77 electrons.
