Study Guide 1 Flashcards
Define an element and compound. How do the two differ? Explain how the compound NaCl exhibits an emergent property distinct from the elements Na or Cl alone.
- element: a substance that cannot be broken down to other substances by chemical reactions
- compound: substances consisting of 2 or more elements
- NaCl exhibits an emergent property distinct from the elements of Na or Cl alone because NaCl is a salt but Na and Cl alone are not salts
List the 4 elements that make up 96% of living matter.
Nitrogen, Carbon, Oxygen, Hydrogen
Distinguish between the mass number and the atomic number of an element.
the mass number is the sum of the protons and neutrons in an atom; the atomic number is the number of protons
Define an isotope. Are all isotopes radioactive? What happens to the ratio of parent isotope to daughter isotope over a single half-life?
- isotope: atoms of an element that have the same atomic number but different has numbers (different amount of neutrons)
- not all isotopes are radioactive; the ones that are, decrease by 50% in a single half-life
The half-life of the carbon isotope, 14C, is about 5700 years. Radioactive dating using14C isotopes found in charcoal used in cave painting by early humans in France shows the cave paintings are about 23,000 years old. Approximately, how much 14C isotope remains in the charcoal?
approximately 6.25%
How does the distribution of electrons in the valence shell of atoms determine the types of chemical bonds the atom is likely to form?
it determines how electronegative the atoms are and if they give up electrons or are likely to take electrons from other atoms to complete its valence shell
Discuss how the valence number coupled with an atom’s electronegativity can be used to predict the type of bonds the atom will form.
it determines how electronegative the atoms are and if they give up electrons or are likely to take electrons from other atoms to complete its valence shell
Which of the following types of bonds have the greatest bond energy?
covalent bonds
Compare and contrast methane (CH4), oxygen (O2), and water (H2O) in terms of polarity, molecular structure and distribution of electrons.
- CH4: nonpolar, one C bonded to 4 H’s, H are partially positively charged
- O2: non polar, 2 Os double bonded, O’s are partially negative
- H2O: polar, one O bonded to two H’s, H’s are partially positively charged, O is partially negatively charged
Compare and contrast sodium chloride to magnesium chloride. What bond holds these salts together?
both salts are held together by ionic bonds
List and describe the weak chemical bonds of Van der Waals interactions and hydrophobic interactions. Discuss the important role that the cumulative effect of weak bonds has on biological molecules.
Van der Waals and hydrophobic interactions are weak bonds that form in fatty acids; they are non polar and repel water; they are easily broken through changes in pH, temperature and force; however they do allow for structural support such as in the tertiary structure of proteins
12 Carbon has ______ protons, ________ neutrons and ________ electrons. How does 12C differ from 14C?
6,6,6; 14C has 6 protons, 8 neutrons, and 6 electrons
How many electrons does carbon need to fill its outer valence shell?
4
Draw the Lewis structure (dot diagram) of Carbon.
:C:
How many covalent bonds can carbon form with other elements?
4
