Chapter 2

Define electronegativity. Which is more electronegative - oxygen or hydrogen? List and describe 5 unique characteristics of water (that relate to water's life-supporting properties!)

- Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. The Pauling scale is the most commonly used - The oxygen atom is more electronegative (it is better than hydrogen at attracting electrons, because it has more positively charged protons in its nucleus), and this makes it slightly more negative; consequently, the hydrogen atoms are unable to hold the electrons near to them, and become slightly more positive. - 5 unique characteristics of water: 1) relatively low viscosity---aquatic animals (marine and freshwater--e.g fish, marine mammals)---can propel through water; also, human blood is comprised mostly of water--the low viscosity allows for easy circulation through the body; 2) water (H2O) is LESS dense in solid form (ice) than its liquid form---due to its lattice structure formed as it freezes---water freezes top to bottom---thus ice floats on liquid water---allowing aquatic life to survive during cold temperatures in deep enough lakes. 3) hydrogen bonding---allows for adhesion and cohesion---capillary action--transport of water through tissues in plants; 4) the so-called "universal solvent"---water dissolves toxins in our bodies; 5) water has a high specific heat capacity---it takes a great deal of energy to heat an entire body of water---or to freeze a large body of water------organisms do not overheat or overcool.

Which of the following solutions has a higher concentration of H+ relative to OH-: acidic solution, neutral solution, basic solution

Acidic solution

What does the atomic number tell you about an atom?What is an isotope? Provide an example. How does this differ from the mass number?

Atomic number is the number of protons in an atom. Isotope is the number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number. For example: Carbon-12, carbon-13, carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively. One is the average weight of an element and the other is the total number of nucleons in the atom's nucleus.

Hydrogen bond

Because they're polarized, two adjacent H2O (water) molecules can form a linkage known as a hydrogen bond, where the (electronegative) hydrogen atom of one H2O molecule is electrostatically attracted to the (electropositive) oxygen atom of an adjacent water molecule. Consequently, molecules of water join together transiently in a hydrogen-bonded lattice. Hydrogen bonds have only about 1/20 the strength of a covalent bond, yet even this force is sufficient to affect the structure of water, producing many of its unique properties, such as high surface tension, specific heat, and heat of vaporization. Hydrogen bonds are important in many life processes, such as in replication and defining the shape of DNA molecules.

Which atoms do all organic molecules contain?

Carbon, hydrogen, oxygen, nitrogen

True or False: Elements are the smallest collection of matter

False: electrons are the smallest particles of matter

What is the difference between the covalent bond that forms methane and the bond that forms water? (in other words, define both polar covalent and nonpolar covalent bonds)

Nonpolar covalent bonds are a type of chemical bond where two atoms share a pair of electrons with each other. Polar covalent bonding is a type of chemical bond where a pair of electrons is unequally shared between two atoms.

Name the three subatomic particles that make up atoms. What charge do they each carry? Which of these are found in the nucleus of an atom? Which are found surrounding the nucleus?

Protons: Positive charge Neutrons: No charges Electrons: Negative charge In the nucleus of an atom, there are Protons and Neutrons Surrounding the nucleus is the Electrons

Covalent bond

The most common bond in organic molecules, a covalent bond involves the sharing of electrons between two atoms. The pair of shared electrons forms a new orbit that extends around the nuclei of both atoms, producing a molecule. There are two secondary types of covalent bonds that are relevant to biology — polar bonds and hydrogen bonds.

Ionic bond

This chemical bond involves a transfer of an electron, so one atom gains an electron while one atom loses an electron. One of the resulting ions carries a negative charge (anion), and the other ion carries a positive charge (cation). Because opposite charges attract, the atoms bond together to form a molecule.