Chemical Basis Of Life

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Chapter 2
Chemical Basis of Life
1. Distinguish between chemistry and biochemistry.
Chemistry is the study of the composition of substances and how they change. Biochemistry is the chemistry of living organisms.
2. Define matter.
Matter is anything that has weight and takes up space.
3. Explain the relationship between elements and atoms.
An element is a basic substance that other things are composed from. Each individual element is made up of tiny, invisible particles called atoms. The atom is the smallest complete unit of an element.
4. Define compound.
A compound is the product of two or more elements being combined.
5. List the four most abundant elements in the human body.
The four most abundant elements are hydrogen, oxygen, carbon, and nitrogen.
6. Describe the major parts of an atom.
Each atom is composed of a central portion, called a nucleus, and one or more electrons that are in constant motion around the nucleus. The nucleus contains one or more large particles called protons, and can also contain one or more similarly-sized particles called neutrons.
7. Distinguish between protons and neutrons.
Protons carry a single, positive electrical charge (p+). Neutrons are uncharged and thus are electrically neutral (n0).
8. Explain why a complete atom is electrically neutral.
The electron carries a single negative electric charge. The protons carry a single positive electric charge. Neutrons carry no charge, thereby making them electrically neutral. The atom is electrically neutral because there is the exact same number of protons and electrons, which effectively cancel each other out.
9. Distinguish between atomic number and atomic weight.
Atomic number represents the number of protons in an atom of a particular element. Since atoms are electrically neutral, it also tells you the number of electrons. Atomic weight represents the number of protons plus the number of neutrons in an atom of a particular element.
10. Define isotope.
Isotopes are elements with the same atomic number but different atomic weights.
11. Define atomic radiation.
Atomic radiation is the energy or atomic fragments that are given off by unstable isotopes.
12. Describe how electrons are arranged within atoms.
The electrons of an atom are found in one or more shells around the nucleus. The maximum number of electrons that each of the first three inner shells can hold is as follows:
First shell (closest to the nucleus) 2 electrons
Second shell 8 electrons
Third shell 8 electrons
13. Explain why some atoms are chemically inert.
An atom is chemically inert when the outermost electron shells are filled. These atoms cannot form chemical bonds.
14. Distinguish between an ionic bond and a covalent bond.
An ionic bond (electrovalent bond) is formed when atoms gain or lose electrons. A covalent bond forms when atoms share electrons.
15. Distinguish between a single covalent bond and a double covalent bond.
A single covalent bond occurs when atoms share one pair of electrons.
A double covalent bond occurs when atoms share two pairs of electrons.
16. Explain the relationship between molecules and compounds.
A molecule is formed when two or more atoms of the same element bond together. A compound is formed when two or more elements of different atoms combine.
17. Distinguish between a molecular formula and a structural formula.
A molecular formula consists of the symbols of the elements in the molecule together with numbers to indicate how many atoms of each element are present. It is essentially the recipe for that particular molecule or compound. A structural formula is drawn to represent how atoms are joined and arranged in various molecules. This is essentially the blueprint of how they fit together.
18. Describe three major types of chemical reactions.
A synthesis reaction occurs when two or more reactants bond together to make a new and more complex product. It can be symbolized as follows: A + B  AB. A