Protons and neutrons are the sub-atomic particles present in the nucleus of an atom where as electrons are present revolving round the nucleus in orbits. Electrons are negatively charged, protons are positively charged where as a neutron is a neutral species. It is the presence of electric charge that lead to the discovery of electrons (negative charge) and protons (positive charge), while it took time to discover neutral as they were electrically neutral species. Neutrons carrying no charge were not detected easily by passing electromagnetic radiations. Therefore, neutrons were the last of the three subatomic particles, to be discovered.
Rare earth metals are a group of 17 elements - lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium - that appear in low concentrations in the ground
Water, Water is not a pure substance. It is a mixture, and Chromatography
Answer: The Answer is minus 221kj.
Explanation: Solved in the attached picture.
