Introductory Chemistry Textbook

Preface to Chemistry Study

• There is a need for better ways to teach and assess students' understanding of the fundamental ideas upon which chemistry is based.
• Need to cultivate an appreciation for how science works and enthusiasm for the beauty, unity, and bizarre processes that make up the natural world.
• Intellectual honesty and rigor, rational and logical discourse, and free and dispassionate analyses, together with compassion and empathy, are critical in the scientific enterprise.

Building a Better Chemistry Book and Course

• Goal is to merge the inherently engaging aspects of chemistry with the active experiences and metacognitive reflections needed to rewire the student’s brain to really understand and accurately use chemical knowledge.
• Presents concepts and skills in various ways, asks students to talk about and work with their understanding, and then ask questions about what students actually mean when they use specific words and ideas.
• Critical to the success of this approach is time: the time required to understand what students think before, during, and after reading the text and working with the applets and activities; the time required for students to recognize and talk about their assumptions; the time required to listen to them, to ask them what, exactly, they mean, and for them to explain, analyze, and where appropriate reconsider, their ideas.

Ancient Ideas and Atomic Theories

• The assumption that the world is ruled solely by natural forces has been remarkably productive, consistent with the way the world appears to behave when we look at it dispassionately.
• In response to more careful observation and experimental analysis, ancient Greek ideas were eventually superseded by more evidence-based theories.
• Most Greek philosophers thought that matter was composed of some set of basic elements, for example, the familiar earth, air, fire, and water.
• Some philosophers proposed the presence of a fifth element, known as quintessence or aether.
• The original elements, that is, earth, air, fire, and water, were thought to be composed of tiny indestructible particles, called atoms by Leucippus and Democritus (who lived around 460 BCE)
• The atoms of different elements were assumed to be of different sizes and shapes, and their shapes directly gave rise to the properties of the particular element.
• The structure of atoms determines the observable properties of the material.
• Atoms were also thought to be in constant motion, based on watching the movement of dust motes in sunlight, with nothing, or a void, between them.
• Einstein's analysis of this type of motion, known as Brownian motion, provided strong experimental support for the physical reality of molecules, larger structures composed of atoms, and the relationship between molecular movement, temperature, and energy.
• All in all the combined notions of the Greek philosophers provided a self-consistent and satisfactory basis for an explanation of the behavior of matter, as far as they could tell.
• A satisfying explanation for a phenomenon is not necessarily true, an explanation is not scientific unless it makes testable, quantitative predictions.
• It is thought that the root of the words alchemy and chemistry is the ancient Greek word Khem, the Greek name for Egypt, where alchemy and chemistry are thought to have originated.
• Ancient ideas about atoms and matter were kept alive by historians and chroniclers, in particular scholars in the Arab world.

Atomic Structure

• Because only a very small percentage of alpha particles were deflected, only a very small region of each atom could be positively charged.
• The positive charge in an atom could not be spread out more or less uniformly, as the plum pudding model assumed; instead it must be concentrated in a very small region.
• Rutherford's model, which became known as the planetary model, postulated a very, very small nucleus where all of the positive charge and nearly all of the mass of the atom was located; this nucleus was encircled by electrons.
• In 1920 Rutherford went on to identify the unit of positive charge and called it the proton.
• In 1932 James Chadwick (1891–1974)(who co-incidentally studied at the University of Manchester) identified a second component of the nucleus, the neutron.
• Neutrons are heavy, like protons.
• Neutrons are slightly heavier than protons but have no charge.
• The identity of the element depends on the number of protons, however the number of neutrons may be different in different atoms of the same element.
• An atom of carbon always has six protons, but it can have different numbers of neutrons.
• Most carbon atoms have six neutrons (C-12), but some have seven (C-13) and some have eight (C-14).

Coulombic Interactions

• Like charges repel and unlike charges attract.
• This interaction, which is known as a Coulombic interaction, depends on the sizes and signs of the charges and is inversely proportional to the square of the distance between them.
• There is a force of attraction (or repulsion if the two charges are of the same sign) that operates between any two charged particles.
• Mathematical description of the electromagnetic interaction is similar to the interaction due to gravity.
• For a gravitational interaction, there must be at least two particles (e.g., you and the Earth) and the force of the attraction depends on both masses and is inversely proportional to the square of the distance between them.
• Gravitational interactions are much weaker than electromagnetic interactions.
• Gravity is solely an attractive interaction, while electromagnetic interactions can be either attractive or repulsive.

Atomic Interactions

• Taken as a whole, atoms are electrically neutral, but they are composed of discrete electrically charged particles.
• Electrons behave as moving objects.
• When averaged over time the probability of finding an electron is spread uniformly around an atom, the atom is neutral.
• At any one instant, however, there is a non-zero probability that the electrons are more on one side of the atom than the other, this results in momentary fluctuations in the charge density around the atom and leads to a momentary charge buildup; for an instant one side of the atom is slightly positive (δ+) and the other side is slightly negative (δ–).
• This produces what is known as an instantaneous and transient electrical dipole - that is a charge separation.
• As one distorted atom nears another atom it affects the second atom’s electron density distribution and leads to what is known as an "induced dipole".

Reasons for needing a new chemistry textbook are explored. The authors support ideals from the Enlightenment. Ancient Greek ideas about the universe are discussed, including the four basic elements.