Bio Chapter 2 Review Flashcards
What is an element? Which elements are most important in organisms?
- substances that can not be broken down by chemical reactions
- elements in organisms: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur
What are the components of an atom, which are charged, which are neutral, and which two are always present in equal number?
atom components: atomic nucleus, electron shell, protons, neutrons, electrons
charged: protons, electrons
neutral: neutrons
equal present: protons and electrons
What component makes the atom of one element different from an atom of another element?
- number of protons (atomic number)
- Atomic number top. mass number bottom
What causes some atoms to be radioactive? What are these types of atoms called?
- different number of neutrons vs protons
- atom is isotope
How many electrons occur in each of the first two shells of an atom? Which electrons possess the highest energy? Which are the valence electrons?
shells: 2 elec (first) 8 elec (second) 18 (third)
valence electrons: electrons in outermost shell
Under what conditions are atoms either stable or chemically reactive? If chemically reactive,
what kind of bonds can they form?
stable: filled valence shell
chemically: unfilled valence shell
chemically bond: covalent bonds -> form molecule
extra: rule of 8s: atoms interact in a way tat they end up having 8 electrons in their valence shell
What is the mechanism for the formation of a covalent bond (what is occurring with the
electrons)? How does a nonpolar covalent bond differ from a polar covalent bond? Why does oxygen tend to form polar covalent bonds with other elements?
mechanism for covalent bond: chemical bonding -> interact to fill their valence shells (electronegativity - likelihood of an atom to attract shared electrons)
nonpolar bond: equal sharing electrons - same electronegativity
covalent bond: unequal sharing electrons - dif electronegativity
oxygen: oxygen atoms attract electrons more than hydrogen and carbon
What is the mechanism for the formation of an ionic bond? What does water do to ionic
bonds? Why does table salt dissolve in water?
ionic bonds: when two atoms have unequal valence electrons -> more electronegative atom will get the electrons from other atom to fill
salt: covalent bonds of water are stronger than ionic bonds of salt
- What is the mechanism for the formation of hydrogen bonds?
- hydrogen is attracted to an electronegative atom - creating a partial negative charge
- weak bond but important
- What are the physical and chemical properties of water that make it important to life?
1) polar molecule (able to bond because of unevenly distributed charge) cohesion: bond to water molecules adhesion: bond to surfaces
2) high specific heat due to hydrogen bonding (heat must be absorbed to break hydrogen bonds)
3) water has high heat for vaporization: hydrogen bonds must be broken to become vapor ex. organisms cool by sweating
4) Water is less dense as a solid than a liquid ex. ice floats, keeps water underneath from freezing - hydrogen bonds do not break when frozen - molecules are certain distance away
5) versatile solvent due to its polarity except to hydrophobic molecules
6) water ionizes
- What is the explanation for water surfaces supporting insects on its surface and for water
creeping up a narrow glass tube?
Water has a high surface tension due to its hydrogen bonding / cohesion with other water molecules.
glass tube: water can also bond with hydrogen bonds o surfaces through adhesion
What is the mechanism and biological significance of the high specific heat and high heat of vaporization of water?
Hydrogen bonding allows water to have a high specific heat - helps heat must be absorbed to break bonds ex. helps to stabilize temp of ocean
Water vaporization helps to control temperature. Vaporization is due to broken hydrogen bonds ex. organisms are cool by sweating
How and why does the density of water change as it is cooled? At what temperature is it most dense and least dense, and what is the explanation?
Density of water changes by how close the hydrogen bonds are from each other. Water is the less dense when frozen because the hydrogen bonds are further apart to hold the ice’s shape
Water is less dense when it is not frozen because the hydrogen bonds are closer to keep high surface tension
How is water structured around a “dissolved” solute? For what two types of solutes is water an excellent solvent, and for what type of solute is it a poor solvent, and why? What makes a molecule hydrophobic or hydrophilic?
Water can disolve solutes because of its polarity which makes it more able to make hydrogen bonds and charge interactions.
Exellent solvent for: ionic and polar solutes
poor solvent: hydrophobic molecules because it is nonionic and nonpolar
hydrophobic: nonpolar molecules that repel water
hydrophilic:polar molecules that love water
What products occur when water ionizes?
positively charged hydronium ion
negative hydroxide ion
