Fundamental particles of an atom

An atom is the smallest unit quantity of an element that is capable of existence, either alone or in chemical combination with other atoms of the same or another element. The fundamental particles of which atoms are composed are the proton, electron and neutron. 

Although chemists tend to consider the electron, proton and neutron as the fundamental (or elementary) particles of an atom, particle physicists would disagree, since their research shows the presence of yet smaller particles. 

Charge number (relative charge) Rest mass/kg Relative mass 

---

In this chapter, I tell you about atoms, the fundamental building blocks of the universe. I cover the three basic particles of an atom — protons, neutrons, and electrons — and show you where they re located. And I use a slew of pages on electrons themselves, because chemical reactions (where a lot of chemistry comes into play) depend on the loss, gain, or sharing of them. 

The cathode ray particle is known today as the electron, a name that comes from the Greek word for amber (electrify, which is a material the early Greeks used to study the effects of static electricity. The electron is a fundamental component of all atoms. All electrons are identical, each having a negative electric charge and an incredibly small mass of 9.1 X 10 31 kilogram. Electrons determine many of a material s properties, including chemical reactivity and such physical attributes as taste, texture, appearance, and color. 

Elements are made of tiny particles called atoms, which can combine in simple numerical ratios according to the law of multiple proportions. Atoms are composed of three fundamental particles Protons are positively charged, electrons are negatively charged, and neutrons are neutral. According to the nuclear model of an atom proposed by Ernest Rutherford, protons and neutrons are clustered into a dense core called the nucleus, while electrons move around the nucleus at a relatively large distance. 

Atom The word comes originally from the Greek word atomos, meaning uncut or indivisible. The ancient Greek philosophers known as the Epicureans believed that matter was composed on small, hard particles they called atomos. The idea and the word was revived in the 1600s to represent the smallest fundamental particle of matter. Today it means the smallest part of an element that can exist independently and interact chemically. 

The smallest particle of an element that maintains its chemical identity through all chemical and physical changes is called an atom (Figure 2-1). In Chapter 5, we shall study the structure of the atom in detail let us simply summarize here the main features of atomic composition. Atoms, and therefore all matter, consist principally of three fundamental particles electrons, protons, and neutrons. These are the basic building blocks of... 

Particles in an Atom Atoms are composed of protons, neutrons and electrons. These are known as fundamental sub-atomic particles. The following table compares the properties of these particles. 

Elements are the fundamental building units of substances. They are composed of tiny particles called atoms atoms are the smallest particles of an element that retains the properties of that element. Atoms are composed of a positively charged nucleus that consists of protons (charge = +1, mass = 1) and neutrons (charge = 0, mass = 1). The nucleus is surrounded by negatively charged electrons that have negligible mass. 

Figure 2.7 shows the location of the elementary particles (protons, neutrons, and electrons) in an atom. There are other subatomic particles, but the electron, the proton, and the neutron are the three fundamental components of the atom that are important in chemistry. Table 2.1 shows the masses and charges of these three elementary particles. 

By the 1930s, however, it was clear that atoms were made up of even smaller particles—protons, neutrons, and electrons, then considered to be the fundamental particles of matter. (A proton is a positively charged particle that weighs about one atomic mass unit [1.0073 AMU] a neutron has about the same mass [1.0087 AMU] but no charge and an electron has a much smaller mass [0.0005 AMU] and a negative charge.) Protons and neutrons make up the tiny nucleus of an atom, while electrons exist outside the atomic nucleus in discrete energy levels within an electron cloud. ... 

The fundamental principle behind analysis by activation analysis is activation or excitation of an atomic nucleus by exposure to radiation such as neutrons, protons or high-energy photons with subsequent measurement of emitted sub-atomic particles or radiation. The most common aspect of the technique involves activation with neutrons in a nuclear reactor and measurement of delayed emitted gamma rays, denoted neutron activation analysis, either instrumental neutron activation analysis (INAA) or neutron activation followed by radiochemical separation (RNAA) in which the element of interest is chemically separated from the matrix after irradiation to provide for better, unimpeded counting. 

We have already seen that a pebble of the kingdom, by which we mean an atom of an element, is a gossamer entity, more space than substance. To be specific, it consists of a massive but minute central nucleus surrounded by almost empty space. That not completely empty space is pervaded by the most important (for chemistry) of nature s fundamental particles, the electron. So our first crude picture of an atom of an element is a speck of a nucleus surrounded by an electron cloud. 

Although the quantum theory of 1925 resolved the age-old dilemma of light by unifying the entities of light and matter and by asserting that wave-particle duality applies to both, it failed to address the issue of another fundamental distinction between the two the photon is created out of nothing—in the flash of an atomic jump—while the electron is permanent. 

---