Flashcards in Chapter 2 - The Chemical Context Of Life + Test Review Deck (63):
Explain why table salt has emergent properties.
Sodium and chlorine bind together to create the compound sodium chloride. Apart, these elements are a metal and a toxic gas; however, together they interact and form the new compound NaCl, showing that it has different properties than a metal and a poisonous gas as it is edible. As the two elements interact they become more complex.
Is a trace element an essential element? Explain.
Yes, as it is required by an organism. However, a trace element is only needed by an organism in minute amounts whereas an essential element is required in larger amounts.
What is an element?
A substance that cannot be broken down into another substance by chemical reactions. Example - gold, carbon, oxygen, copper, etc. The most basic form.
What is a compound?
A substance consisting of two or more different elements combined in a fixed ration. A compound has characteristics that are different than its elements. Example - NaCl (Sodium chloride, table salt) H2O (Water).
What are essential elements? What are the four essential elements in the human body?
Essential elements are required for an organism to live, survive, and reproduce. The four elements 1) Oxygen, O 2) Carbon C 3) Hydrogen H and 4) Nitrogen N, account for 96% of living matter.
What are trace elements? Give some examples.
Trace elements are required by an organism, but only in minute quantities. Example - Calcium Ca, Potassium K, Sodium Na, Magnesium Mg, etc.
In humans, iron is a trace element required for the proper functioning of hemoglobin, the molecule that carries oxygen in red blood cells. What might be the effects of an iron deficiency?
An effect of low oxygen levels can be fatigue. Anemia.
Explain how natural selection might have played a role in the evolution of species that are tolerant of serpentine soils.
The plants adapted with an ability to tolerate elevated levels of the elements in serpentine soils and could then grow and reproduce there. The offspring of these plants would vary, with the most capable of thriving under serpentine conditions growing best and reproducing most. Many generations continued to adapt like this.
A lithium atom has 3 protons and 4 neutrons. What is its mass number?
A nitrogen atom has 7 protons, and the most common isotope of nitrogen as 7 neutrons. A radioactive isotope of nitrogen has 8 neutrons. Write the atomic number and mass number of this radioactive nitrogen as a chemical symbol with a subscript and superscript.
N - atomic number 7 - mass number 15
How many electrons does fluorine have? How many electron shells? Name the orbitals that are occupied. How many electrons are needed to fill the valence shell?
A) 9 electrons
B) 2 shells
C) 1s, 2s, 2p - three orbitals
D) 1 electron is needed to fill the valence shell
In Figure 2.7 (Periodic Table showing electron distribution), if two or more elements are in the same row, what do they have in common? If two ore more elements are in the same column, what do they have in common?
A) The number of electron shells
B) The number of valence electrons in their valence shells
What do an elements properties depend on?
The structure of the atom.
What is the definition of an atom? What 3 subatomic particles make up an atom? What are their electronic charges?
The smallest unit of matter that retains the properties of the element. 1) Proton - 1 unit of positive charge, 2) neutron - electrically neutral, and 3) electron - 1 unit of negative charge.
What is an atomic nucleus?
Protons and neutrons packed together in a dense core at the center of an atom.
What is an electron? Explain how it works, basically.
A subatomic particle that holds 1 unit of negative charge. Electrons form a cloud of negative charge around the nucleus and the attraction of opposite charges keeps the electrons in the vicinity of the nucleus.
What is the unit used to measure the mass of subatomic particles?
Dalton - or atomic mass unit. Neutrons and protons have a mass close to 1 dalton.
What is an atomic number?
The number of protons which is unique to that element (written to the left of the symbol for that element). All atoms of a particular element have the same number of protons in their nuclei. *Extra - Unless otherwise noted, an atom is neutral in electrical charge, meaning protons must be balanced by an equal amount of electrons.*
What is the mass number?
The sum of protons and neutrons in the nucleus. (Written to the left of the element symbol on top of the atomic number).
What is atomic mass?
The total mass of an atom. Actually, an average of the atomic masses of all the element's naturally occurring isotopes.
What are isotopes?
The different atomic forms of the same element. All atoms of a given element have the same number of protons, but some atoms have more neutrons than other atoms of the same element and therefore have a greater mass. *Even though isotopes have slightly different masses, they behave identically in different chemical reactions.*
What is a radioactive isotope?
One in which the nucleus decays spontaneously. When this decay changes the number of protons, it transforms the atom to a different element. Example - when (^14)C (carbon) decays, it becomes (^14N) (nitrogen)
Explain "half life".
A "parent" isotope decays into its "daughter" isotope at a fixed rate and is expressed as the "half life" of the isotope. The amount of time it takes for 50% of a sample of radioactive isotope to decay.
Explain radiometric dating.
Radiometric dating measures the ratio of different isotopes and can calculate how many "half lives" (in years) have passes since the organism was fossilized.
What is energy?
The capacity to cause change.
What is potential energy?
The energy that matter possesses because of its location or structure. *The more distant an electron is from the nucleus, the greater its potential energy.*
What is an electron shell?
An energy level of electrons at a characteristic average distance from the nucleus of an atom. Show in 2D as concentric circles surrounding the nucleus. *When an electron absorbs energy, it moves to a shell further out from the nucleus.*
What is a valence electron?
An electron in the outermost electron shell.
What is the valence shell?
The outermost electron shell of an atom.
Explain electron ORBITALS.
An orbital is the 3D space where an electron is found 90% of the time. The first electron shell has only one spherical s orbital (called 1s), but the second shell has four orbitals: one large spherical s orbital (called 2s) and three dumbbell shaped p orbitals (called 2p orbitals). The third shell and other higher electron shells also have s and p orbitals, as well as orbitals of more complex shapes.
Why does the structure H - C = C - H fail to make sense chemically?
Each carbon atom has only three covalent bonds instead of the required four.
What holds the atoms together in a crystal of magnesium chloride (MgCl2)?
The attraction between oppositely charged ions, forming ionic bonds.
If you were a pharmaceutical researcher, why would you want to learn the 3D shapes of naturally occurring signaling molecules?
If you could synthesize molecules that mimic these shapes, you might be able to treat diseases or conditions caused by the inability of affected individuals to synthesize such molecules. Example - endorphins and morphine.
Explain how atoms interact.
Atoms with incomplete valence shells interact with other atoms in such a way that each partner completes its valence shell. (Share or transfer valence electrons)
What is a chemical bond?
An attraction between 2 atoms resulting from a sharing of outer shell electrons or the presence of opposite charges in atoms. The bonded atoms gain complete outer electron shells. The strongest chemical bonds are called covalent bonds.
What is a covalent bond?
The sharing of a pair of valence electrons by two atoms.
What is a molecule?
2 atoms held together by a covalent bond. Example - H1 + H1 = H2.
What is a single bond?
A pair of shared valence electrons by 2 atoms.
What is a double bond?
A double covalent bond. The sharing of 2 pairs of valence electrons by 2 atoms.
Explain valence. What are the valences of hydrogen, oxygen, nitrogen, and carbon?
The bonding capacity is called the atoms valence and usually equals the number of unpaired electrons required to complete the valence shell. H = 1, O = 2, N = 3, C = 4
What is methane?
1 carbon atom bonds with 4 hydrogen atoms. CH4
The attraction of a particular atom for the electrons of a covalent bond. The more electronegative an atom is, the stronger it pulls shared electrons toward itself.
What is a non polar covalent bond?
A covalent bond between 2 atoms of the same element. The electrons are shared equally because the 2 atoms have the same electronegativity. Example - H2, O2
What is a polar covalent bond?
This type of bond happens when an atom is bounded to a more electronegative atom. The electrons of the bond are not shared equally. *Oxygen is one of the most electronegative elements*
What are ions? What are the 2 types of ions?
Opposite charged atoms. An atom or group of atoms that has gained or lost one or more electrons, thus acquiring a charge. 1) cation - positively charged, 2) anion - negatively charged.
What is an ionic bond?
Two ions of opposite charge attracted to each other. Example - NaCl
What are ionic compounds?
(Salts) Compounds formed by ionic bonds and does not consist of molecules.
What is a hydrogen bond?
An attraction between a hydrogen and an electronegative atom. (Electronegative partners are usually oxygen or nitrogen). Example - Ammonia (NH3) + Water (H2O) - Results from the attraction between the partial positive charge on the hydrogen atom of water and the partial negative charge on the nitrogen atom of ammonia.
Explain van dear Waals interactions.
Weaker attractions between molecules or parts of molecules that result from transient local partial charges. (Occur only when molecules and atoms are close together)
Give an example of molecular shape and how that affects function. Why is it important?
Shapes of atoms and molecules depend on positions of atoms orbitals. Molecular shape is crucial as it determines how biological molecules recognize and respond to one another with specificity. Structure affects the function. Example - morphine and endorphins.
When is an element inert and non-reactive?
When the element has a complete valence shell.
How do radioactive elements become stable?
In order to radioactive elements to stabilize, they omit rays of energy. *Example - alpha, beta, or gamma rays (gamma being the harshest and most damaging)
Figure 2.10 - Covalent bonding.
See photos for diagram.
Which type of chemical reaction occurs faster at equilibrium, the formation of products from reactants or reactants from products?
At equilibrium, the forward and reverse reactions occur at the same rate.
Write an equation that uses the products of photosynthesis as reactants and the reactants of photosynthesis as products. Add energy as another product. This new equation describes a process that occurs in your cells. Describe this equation in words. How does this equation relate to breathing?
C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + Energy. Glucose and oxygen react to form carbon dioxide and water, releasing energy. We breathe in oxygen because we need it for this reaction to occur, and we breathe out carbon dioxide because it is a byproduct of this reaction.
What are chemical reactions?
The making and breaking of chemical bonds. *Matter is conserved in a chemical reaction as reactions cannot create or destroy atoms but can only rearrange or redistribute the electrons among them.*
What is a reactant?
The starting material in a chemical reaction. Example - H2 or O2
What is a product?
The material resulting from a chemical reaction. Example - H2O
What is the chemical shorthand for photosynthesis?
6 CO2 (carbon dioxide) + 6 H2O (water) --> C6H12O6 (glucose) + 6 O2 (oxygen)
Discuss the reversibility of reactions.
All chemical reactions are reversible, with the products of the forward reaction becoming the reactants for the reverse reaction. Example - 3 H2 (hydrogen) + N2 (nitrogen) -->--
Explain chemical equilibrium.
Chemical equilibrium is reached when the forward and reverse actions occur at the same rate. The relative concentrations of products and reactants stop changing and the reactions offset one another exactly.
What are the 3 weak bonds that hold complex molecules together?
1. Ionic bond - exists between ions dissociated in water
2. Hydrogen bond - the attraction between a hydrogen and an electronegative atom
3. Van der waals interactions - electrons accumulate by chance in one part of a molecule distributing unevenly. The results are ever changing regions of positive and negative charge that enable all atoms and molecules to stick to one another. These interactions are individually weak and occur only when atoms and molecules are very close together