2: Naming and Structure of Compounds
- Page ID
- 466576
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- 2.1: Subatomic Particles - Electrons, Protons, and Neutrons
- Now that we know how atoms are generally constructed, what do atoms of any particular element look like? What types of particles are contained inside an atom? In this section, we will explore the three subatomic particles most atoms contain. Experiments in the late 19th and early 20th centuries helped to define and locate each of these three atomic pieces. Overviews of these experiments will help you to appreciate the efforts involved to explain the structure of the atom.
- 2.2: Atomic Number and Mass Number
- Atoms are the fundamental building blocks of all matter and are composed of protons, neutrons, and electrons. Because atoms are electrically neutral, the number of positively charged protons must be equal to the number of negatively charged electrons. Since neutrons do not affect the charge, the number of neutrons is not dependent on the number of protons and will vary even among atoms of the same element.
- 2.3: Isotopes
- Isotopes are atoms of the same element that differ in the amount of neutrons and atomic mass. Almost all elements on the periodic table have at least two different natural isotopes. Many elements have synthetic isotopic forms that have been made by nuclear chemists and/or physicists. Chemically, isotopes appear to be the same. For example, the two most abundant forms of uranium look physically the same and react to other materials in a similar manner.
- 2.4: The Importance of Ions to a Chemist
- Chemists appreciate isotopes and use them in basic and applied research. However, they are more concerned with the movement of electrons. When an atom gains or loses electrons, it becomes a charged species or an ion. When this occurs, the nucleus is not altered. For atoms that lose electrons, an overall positive charge will result (#protons > #electrons). Atoms that form these types of ions are called cations.
- 2.5: Lewis Dot and Bonding
- Why are some substances chemically bonded molecules and others are an association of ions? The answer to this question depends upon the electronic structures of the atoms and nature of the chemical forces within the compounds. Although there are no sharply defined boundaries, chemical bonds are typically classified into three main types: ionic bonds, covalent bonds, and metallic bonds.
- 2.6: Ionic Formula Writing
- So far, we have discussed elements and compounds that are electrically neutral. They have the same number of electrons as protons, so the negative charges of the electrons is balanced by the positive charges of the protons. However, this is not always the case. Electrons can move from one atom to another; when they do, species with overall electric charges are formed. Such species are called ions.
- 2.7: Covalent Bonding and Formula Writing
- In ionic bonding, electrons are transferred from one atom to another so that both atoms have an energy-stable outer electron shell. Because most filled electron shells have eight electrons in them, chemists called this tendency the octet rule. However, there is another way an atom can achieve a full valence shell: atoms can share electrons. This type of bonding would be a covalent bond.
- 2.8: Molar Mass to Mole Conversions
- Conversations about compounds often require a way to discuss the relative number of each atom, molecule, or compound; but the mass of these components can vary greatly. Making things more difficult is the extremely small size of these components. Scientists use the unit "mole" to represent a large number of items. Converting between molar mass and moles is a very useful tool, especially when transitioning to experiments in the laboratory.
- 2.9: Chemical Equations
- A chemical reaction is described by a chemical equation that gives the identities and quantities of the reactants and the products. In a chemical reaction, one or more substances are transformed to new substances. A chemical reaction is described by a chemical equation, an expression that gives the identities and quantities of the substances involved in a reaction. A chemical equation shows the starting compound(s)—the reactants—on the left and the final compound(s)—the products—on the right.