Unit 2 Study Guide: Basic Chemistry

2a. List the major components of an atom and their locations.

The universe is made up of matter and energy. Matter (all of the material in the universe) is made up of almost unimaginably small particles called atoms. As tiny as atoms are, there are even smaller particles that make up each atom. Since they are smaller than atoms, we call them "subatomic particles".

  • What are the three primary subatomic particles?
  • What are the major differences between the various subatomic particles?
  • Where are the various subatomic particles located within an atom?

The primary subatomic particles are protons, neutrons, and electrons. Protons and neutrons make up the nucleus of an atom. Electrons are found outside the nucleus. A proton has an electrical charge of +1. A neutron is nearly identical in size to a proton, but it has no charge. An electron is much smaller than a proton or neutron. An electron is also a charged particle. Despite being much smaller than a proton, the charge of an electron is equal in magnitude to the charge of a proton. However, the charge is opposite, so each electron has a charge of -1.

  • What is an electron shell?
  • What is a subshell?
  • What is an orbital?

Electrons occupy spaces around the nucleus. These spaces have a hierarchical arrangement. An orbital is a space that can be occupied by electrons. Each orbital can contain up to two electrons. There are different types and shapes of orbitals: s,p,d, and f. There is only one kind of s orbital, but there are three kinds of p orbital, five d orbitals, and seven f orbitals. A collection of orbitals of the same type makes up a subshell, and a collection of subshells makes up a shell (also called an energy level). The first shell includes only one subshell (the s subshell), which is made up of only one s orbital. The second shell is made up of two subshells (an s and a p subshell), with the s subshell being made up of one s orbital and the p subshell being made up of three p orbitals. Since different shells contain different numbers of orbitals, each shell has a different maximum number of electrons it can hold.

You can review atomic structure and orbitals by watching these lectures.

 

2b. List the different types of bonds and how they lead to the formation of molecules and compounds.

Atoms are the building blocks of elements, which are pure substances made up of only one kind of atom. Though there are just over one hundred different elements, there are countless different substances in the universe. Most of these substances are not elements; rather, they are compounds.

  • What is a compound?
  • How is a compound different from an element?
  • How are compounds formed?

A compound is a substance made up of two or more different kinds of atoms. This is the fundamental distinction between an element and a compound. Rather than simply being a mixture of two or more kinds of atoms, compounds are formed when different kind of atoms interact. That interaction gives the compound different properties compared to the properties of the constituent elements. For example, sodium chloride (table salt) is made up of the elements sodium and chlorine, but sodium chloride (the compound) is different from both of those elements. The interactions between atoms in a compound are called chemical bonds. There are three major categories of chemical bonds:

  • Ionic bonds form when one or more electron from one atom is transferred to another atom, creating a positive ion and a negative ion that are attracted to each other because of their opposite charges.
  • Covalent bonds form when one or more pairs of electrons are shared by two different atoms, holding the two atoms together more strongly than an ionic bond.
  • Metallic bonds consist of a "sea" of electrons that move about from one metallic atom to another, holding together many metallic atoms.

Molecules are particles that are bigger than atoms. They are made up of multiple atoms (of either the same or different elements) held together by covalent bonds. A molecule of water, for example, consists of an oxygen atom covalently (and separately) bonded to two hydrogen atoms.

It’s important to appreciate the distinction between atoms, ions, molecules, elements, and compounds. Viewing this lecture will help you review.

 

2c. Describe the primary concepts of thermodynamics as they relate to heat, temperature, energy, and work.

Thermodynamics is a branch of science concerned with energy and its transfer between objects. Thermodynamics applies throughout the universe, but thermodynamics is studied within biology, because organisms involve many energy transactions. In other words, organisms are thermodynamic systems.

  • What is energy?
  • What is heat?
  • What is temperature?
  • What is work?
  • What are the laws of thermodynamics?

These are fundamental questions of thermodynamics. Energy is often defined as the capacity to do work. Work refers to some sort of change. For instance, moving an object from one place to another requires work, and energy is required for that work. Heat is energy in the form of movement of particles (atoms, ions, or molecules) within a substance. Heat is energy that is unavailable for performing work. Temperature is a measure of the average speed of the particles in an object. Temperature and heat are not the same thing. Temperature does not depend on how much matter is present, whereas heat does. For example, a swimming pool has the same temperature as a cup of water from that swimming pool, but the swimming pool contains much more heat than the cup of water, because it contains much more matter.

There are four laws of thermodynamics, and two of those are important in biology:

  • The first law of thermodynamics states that energy cannot be created or destroyed, though it can be transferred and transformed. This is also known as the law of conservation of energy.
  • The second law of thermodynamics states that every energy transaction increases the entropy (disorder) of the universe. An implication of this second law is that every energy transaction involved some loss of usable energy as heat, so no energetic process (including those occurring in organisms) can ever be perfectly efficient.

As you proceed to study living things, these thermodynamic concepts will be important, so be sure review them in this lecture and this chapter.

 

Unit 2 Vocabulary

This vocabulary list includes terms that might help you with the review items above and some terms you should be familiar with to be successful in completing the final exam for the course.

Try to think of the reason why each term is included.

  • Atom
  • Chemical Bond
  • Compound
  • Covalent Bond
  • Electron
  • Element
  • Energy
  • Heat
  • Ion
  • Ionic Bond
  • Metallic Bond
  • Molecule
  • Neutron
  • Orbital
  • Proton
  • Shell
  • Subshell
  • Temperature
  • Thermodynamics
  • Work
Last modified: Wednesday, July 17, 2019, 5:48 PM