BIO101 Study Guide

Unit 2: Basic Chemistry

2a. List the major components of an atom and their relative locations to one another

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?
What is an electron shell, a subshell, and an orbital?

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

The primary subatomic particles are protons, neutrons, and electrons. Protons and neutrons make up the nucleus of an atom. Electrons are 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 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.

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.

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2b. Describe how chemical attraction creates bonds of varying strengths

What are the different types of chemical bonds?
How is the strength of each bond different from one another?
How can you relate the strength of a bond to the type of chemical attraction between its parts?
What type of chemical interaction creates the strongest bonds? …the weakest bonds?

All biological systems rely on chemical bonds of various types. Bond strength is relative to the type of interaction between its parts.

From lowest to highest strength, these bonds are:

Van der Waals forces are relatively weak and temporary attractions between molecules, creating temporary dipoles.
Dipole-dipole interactions are stronger due to the attraction of negative and positive ends of different molecules.
Hydrogen bonds are stronger yet still considered weak bonds; they form between a hydrogen atom (which has one proton) and another negative atom.
Metallic bonds are stronger than hydrogen bonds. They form a "sea" of electrons among metal atoms, allowing for the conduction of electricity and heat.
Ionic bonds are stronger yet and are created between atoms that transfer electrons among themselves, creating opposite attracting charges.
Covalent bonds are the strongest type of bonds, created when atoms share electrons between them, creating a stable bond. The bond can be single (sharing of one pair of electrons), double (sharing two pairs), or triple (sharing three pairs).

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

What is a compound, and how does a compound differ from a molecule?
How does a compound differ from an element?
What hierarchy is involved between atoms, elements, molecules, and compounds?
How are compounds formed?

Atoms are the building blocks of elements, which are pure substances made of one kind of atom. Although there are just more than 100 elements, there are countless substances in the universe. Most of these substances are compounds, not elements.

A compound is a substance made 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 kinds of atoms interact. This interaction gives the compound different properties compared to the properties of the constituent elements.

For example, sodium chloride (table salt) is made of the elements sodium and chlorine, but sodium chloride (the compound) is different from each of these 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 electrons from one atom are transferred to another atom, creating a positive ion and a negative ion that are attracted to each other because of their opposite charges. Ions are charged elements.
Covalent bonds form when two different atoms share one or more pairs of electrons, which hold 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 bigger than atoms. They are made of multiple atoms (of the same or different elements) held together by covalent bonds. For example, a molecule of water consists of an oxygen atom that is covalently and separately bonded to two hydrogen atoms.

You should appreciate the distinction between atoms, ions, molecules, elements, and compounds.

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

What are energy, heat, temperature, and work?
Can you name and describe the laws of thermodynamics?

Thermodynamics is the branch of science concerned with energy and energy transfer between objects. Although thermodynamics applies throughout the universe, we study it within biology because organisms are involved in many energy transactions. In other words, organisms are thermodynamic systems.

These are fundamental questions of thermodynamics. We can define energy as the capacity to do work. Work refers to some sort of change. For example, 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.

Two of the four laws of thermodynamics 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 involves some loss of usable energy as heat, so no energetic process (including those occurring in organisms) can ever be 100 percent efficient.

These thermodynamic concepts are important for understanding the biochemistry of living things.

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Unit 2 Vocabulary

This vocabulary list includes terms you will need to know to successfully complete the final exam.

chemical bond
covalent bond
dipole-dipole interaction
electron
energy
energy level
entropy
First Law of Thermodynamics
heat
hydrogen bonds
ion
ionic bond
Law of Conservation of Energy
matter
metallic bond
neutron
orbital
proton
Second Law of Thermodynamics
shell
subatomic particle
subshell
temperature
thermodynamics
Van der Waals force
work