Atoms subatomic particles

Subatomic particle A particle that is smaller than an atom. Subatomic particles include protons, neutrons, electrons, quarks, photons, neutrinos, and muons. 

The atom is now known to consist of three primary particles protons, neutrons, and electrons, which make up the atoms of all matter. A series of experimental facts established the validity of the model. Radioactivity played an important part. Marie Curie suggested, in 1899, that when atoms disintegrate, they contradict Dalton s idea that atoms are indivisible. There must then be something smaller than the atom (subatomic particles) of which atoms were composed. 

Chapter 4, Atoms and Elements, looks at elements, atoms, subatomic particles, atomic numbers, and mass numbers. Using the naturally occurring isotopes and abundances, atomic mass is calculated. 

As you probably know, an atom consists of a dense, positively charged nucleus surrounded at a relatively large distance by negatively charged elections (Figure 1.2). The nucleus consists of subatomic particles called neutrons, which are electrically neutral, and protons, which are positively charged. Because an atom is neutral... 

The observation that atoms of a single element can have different masses helped scientists refine the nuclear model still further. They realized that an atomic nucleus must contain subatomic particles other than protons and proposed that it also contains electrically neutral particles called neutrons (denoted n). Because neutrons have no electric charge, their presence does not affect the nuclear charge or the number of electrons in the atom. However, they do add substantially to the mass of the nucleus, so different numbers of neutrons in a nucleus give rise to atoms of different masses, even though the atoms belong to the same element. As we can see from Table B.l, neutrons and protons are very similar apart from their charge they are jointly known as nucleons. 

B.9 An unstable atomic nucleus gives off nuclear radiation consisting of particles that have a mass of about 1.7 X 10 kg. The particles are attracted to a negatively charged plate. The radiation consists of what type of subatomic particle ... 

B.10 (a) What characteristics do atoms of carbon-12, carbon-13, and carbon-14 have in common (b) In what ways are they different (Consider the numbers and types of subatomic particles.)... 

Dalton pictured atoms as featureless spheres, like billiard balls. Today, we know that atoms have an internal structure they are built from even smaller subatomic particles. In this book, we deal with the three major subatomic particles the electron, the proton, and the neutron. By investigating the internal structure of atoms, we can come to see how one element differs from another and see how their properties are related to the structures of their atoms. 

The earliest experimental evidence for the internal structure of atoms was the discovery in 1897 of the first subatomic particle, the electron. The British physicist... 

The uncertainty principle has negligible practical consequences for macroscopic objects, but it is of profound importance for subatomic particles such as the electrons in atoms and for a scientific understanding of the nature of the world. 

Chemical advances frequently are driven by technology. The discovery that atoms have inner structure was an outgrowth of the technology for working with radioactive materials. In Chapter 2 we describe a famous experiment in which the structure of atoms was studied by bombarding a thin gold foil with subatomic particles. A contemporary example is the use of lasers to study the details of chemical reactions. We introduce these ideas in Chapters 7 and 8. 

Neutron A subatomic particle found in the nuclei of atoms. It is electrically neutral with a mass that is slightly greater than that of a proton. 

Proton The positively charged subatomic particle found in the nucleus of atoms. 

Electron A negatively charged subatomic particle found traveling around the outside of an atom s nucleus in energy levels, or shells. 

From 50 years to 100 years after Dalton proposed his theory, various discoveries showed that the atom is not indivisible, but really is composed of parts. Natural radioactivity and the interaction of electricity with matter are two different types of evidence for this subatomic structure. The most important subatomic particles are listed in Table 3-2, along with their most important properties. The protons and neutrons occur in a very tiny nucleus (plural, nuclei). The electrons occur outside the nucleus. 

EXAMPLE 3.3. Refer to Tabic 3-2 and deduce which two of the types of subatomic particles in an uncombincd atom occur in equal numbers. 

The number of which subatomic particle is different in atoms of two isotopes ... 

Ans. (a) The nucleus is a distinct part of the atom. Neutrons are subatomic particles which, along with protons, are located in the nucleus. (b) Mass number refers to individual isotopes. It is the sum of the numbers of protons and neutrons. Atomic weight refers to the naturally occurring mixture of isotopes, and is the relative mass of the average atom compared to l2C. (/) Atomic mass is the same as atomic weight [see (b)]. Atomic mass unit is the unit of atomic weight. 

All of the artificial elements prepared thus far are radioactive. That is, of their own accord, they break down into elements of different atomic number, often with the release of tremendous quantities of energy. A few of the first 92 elements are also radioactive. They have unstable nuclei which often shoot out particles as radiation. Radiation is the name for various rays of subatomic particles given off by radioactive elements. 

The internal structure of the atom, that is, how the subatomic particles are arranged in space within the atom, is very complicated. All the protons, plus varying numbers of electrically neutral particles called neutrons, cluster inside the central nucleus. The 1... 

A look at die atom and the subatomic particles and forces which hold it together or break it apart.)... 

If we assume that the mass of the atom is simply the sum of the masses of its subatomic particles, then... 

Natural radioactivity derives from spontaneous nuclear disintegrations. Induced radioactivity derives from the bombardment of nuclei with accelerated subatomic particles or other nuclei. Both cause atoms of one nuclide to be converted to another nuclide. 

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