Number of Subatomic Particles

One very important component of the study of the subatomic particles in atoms is the number of each of these particles within an atom and how one element s atoms differs from another element s atoms in terms of this number. In Section 1.4.1, we indicated that the atoms of different elements are different from each other, noting, for example, that the size of a francium atom compared with the size of a hydrogen atom is like comparing a basketball with a pingpong ball. Besides size, they also differ in terms of the number of protons, neutrons, and electrons that each has. 

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Explain how you would design a data base to display information about the atomic numbers, atomic masses, the number of subatomic particles, and the number of electrons in the outer energy levels of the main-group elements. If you have access to spreadsheet software, construct this table. 

The new work led to a physical definition of an element based on atomic structure. According to the physical definition of an element, all the atoms of a particular element have the same number of protons and electrons, although the number of neutrons may vary. The placement of the protons, electrons, and neutrons in the atom follow strict rules of arrangement. The number of subatomic particles and their arrangement then determines the way atoms of elements interact. 

Estimate the percentage of the total mass of a 29CU atom that is due to (a) electrons, (b) protons, and (c) neutrons by assuming that the mass of the atom is simply the sum of the masses of the appropriate numbers of subatomic particles. 

SAMPLE PROBLEM 2.2 Determining the Number of Subatomic Particles... 

The investigation of cosmic radiation has had a profound influence on nuclear science. When Chadwick in 1932 discovered the neutron, the picture of matter seemed complete all matter appeared to be composed of four fundamental particles protons, neutrons, electrons, and photons. However, through studies of the cosmic radiation Anderson discovered the positron (the first antiparticle) in the same year. Five years later Anderson and Neddermeyer discovered another new particle with a mass about one-tenth of a proton or about 200 times heavier than the electron. This particle is the muon, designated by p. Since that time a large number of subatomic particles have been discovered. 

All atoms are made up of protons, neutrons, and electrons. Because these particles are Ihe same in all atoms, the difference between atoms of distinct elements (gold and oxygen, for example) is due entirely to the difference in file number of subatomic particles in each atom. We can fiierefore consider an atom to be tile smallest sample of an element because breaking an atom into subatomic particles destroys its identity. 

Use the concepts of atomic number and mass number to determine the number of subatomic particles in isotopes and to write correct symbols for isotopes. (Section 2.3)... 

To discuss nuclear reactions in any depth, we must understand how to write and balance nuclear equations. Writing a nuclear equation differs somewhat from writing equations for chemical reactions. In addition to writing the symbols for the various chemical elements, we must also explicitly indicate the number of subatomic particles in every species involved in the reaction. 

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