Lester Leslie, age 12, of Des Moines, Iowa, for his question:
What is in the atomic nucleus?
The nucleus is the hard and heavy core at the center of the atom. Without the nucleus, the atom would be a mere jumble of particles. Yet this central powerhouse takes up only a small part of the atom. If the atom were as big as a football stadium, the nucleus would be no bigger than a golf ball. In the space around it there would be up to 100 orbiting electron particles • on this scale no bigger than flies.
Though most of the atom is empty spacep the central nucleus is very dense indeed. If we could strip away the space and make a penny from the closely packed nuclei, our coin would weigh many millions of tons, Fortunately the nucleus of an atom is very small. It takes about 100 million carbon atoms to measure one inch. The diameter of each one of those atoms is 30,000 times greater than the diameter of its nucleus.
Small as it is, the atomic nucleus is made from even smaller particles. Every nucleus has a very definite number of protons. These atomic particles each have a single charge of positive electricity. Almost all nuclei also have a number of neutrons. These particles are the same weight and size as the protons but they are electrically neutral.
The character of an atom depends entirely upon the number of protons in its nucleus, Every atom of hydrogen, the smallest of atoms, has one and only one proton. Every atom of oxygen has eight protons, told has
79 protons. Should an atom lose or gain a proton in its nucleus, it becomes an atom of something else. Each element gets its atomic number from the number of protons in the nucleus. The atomic number of hydrogen is 1. Oxygen has atomic number 8 and gold has atomic number 79.
Also present among the highly charged protons are a number of neutron particles. It has been suggested that these neutral particles act as policemen among the particles of positive electricity. The hydrogen atom, with but one protons has no neutron. Helium, with two proton, has two neutrons. Lithium, with three protons, may have three or four neutrons. The mass number of an atom is the number of protons and neutrons in the nucleus. The mass number of hydrogen is 1, of helium 4. The mass number of a rare type of lithium is 6, the more common type is mass number
The weight of an atom includes the nucleus, plus the orbiting electrons. In a healthy atom, the number of negatively charged electrons equals positive protons, However, one proton or one neutron weighs as much as 1800 electrons. About 99.9 per cent of the atom's weight is in the nucleus, no bigger comparatively than a golf ball in a stadium.