Chapter 2: Atoms, Molecules, and Life

Ionic bonds

A chemical bond formed by the electrical attraction between positively and negatively charged ions.

Base

1) A substance capable of combining with and neutralizing H+ ions in a solution; a solution with a pH greater than 7. 2) One of the nitrogen-containing single- or double-ringed structures that distinguishes one nucleotide from another. In DNA the nucleotides are adenine, guanine, cytosine, and thymine.

What are the two basic principles in which atoms behave?

1) An atom whose outermost electron shell is completely full will not react with other atoms. Such an atom is extremely stable and is described as inert. 2) An atom whose outermost electron shell is partially full will react readily with other atoms. Such an atom is described as reactive.

Ion

A charged atom or molecule; an atom or molecule that either has an excess of electrons (and therefore has a negative charge) or has lost electrons (and therefore positively charged). *Ions with opposite charges attract one another

Periodic table

A chart first devised by Russian chemist Dmitri Mendeleev that includes all known elements and organizise them according to their atomic numbers in rows and their general chemical proerties in columns.

Covalent bonds

A chemical bond between atoms in which electrons are shared. *The atoms in most biological molecules , such as proteins, sugars, and fats are joined by covalent bonds.

Buffer

A compound that minimizes changes in pH by reversibly taking up or releasing H+ ion.

Nonpolar covalent bonds

A covalent bond with equal sharing of electrons.

Polar covalent bonds

A covalent bond with unequal sharing of electrons, such that one atom is relatively negative and the other is relatively positive.

Solvent

A liquid capable of dissolving (uniformly dispersing) other substances within itself.

Molecules

A particle composed of one or more atoms held together by chemical bonds; the smallest particle of a compaound that displays all the properties of that compound.

Chemical reaction

A process that forms and breaks chemical bonds that hold atoms together n molecules.

Electron shells

A region within the atom which electrons orbit; each shell corresponds to a fixed energy level at a given distance from the nucleus. *Each shell can hold a specific number of electrons. The shell nearest the nucleus can only hold two electrons and more distant shells can hold eight or more. *Electrons will always fill the lowest levels first.

pH scale

A scale, with values ranging from 0 to 14, used for measuring the relative acidity of a solution; at pH 7 a solution is neutral, at pH 0 to 7 is acidic, and pH 7 to 14 is basic; each unit on the scale represents a tenfold change in H+ consentration.

Solution

A solvent containing one or more dissolved substances (solutes).

Element

A substance that cannot be broken down, or converted, to a simpler substance by ordinary chemical reactions.

Acid

A substance that releases hydrogen ions (H+) into solution; a solution with a pH less than 7.

Although the forest is growing quickly around Chernobyl, and some of the wildlife is thriving, studies show that biodiversity around Chernobyl has been reduced by over 50% since the accident. Why? A) The ionizing radiation affects the DNA of the wildlife, just as it affects the DNA of humans. B) Humans are no longer present to feed the wildlife. C) The constant intrusion by reporters has lead to a decline in many species of animals. D) The radioactive cloud overhead blocks the sunlight.

A) The ionizing radiation affects the DNA of the wildlife, just as it affects the DNA of humans.

Free radicals

An atom containing an atom with an unpaired electron, which makes it highly reactive and unstable with nearby molecules. By removing an electron with the molecule it attacks, it creates a new free radicle and begins a chain reaction that can lead ti the destruction of biological molecules crucial to life. *Free radicals are produced in large numbers in the body by reactions that make energy available to cells. Although these reactions are essential to life, over time, the stress that free radicals place on living cells may contibute to againg and even death.

Chemical bond

An attraction between two atoms or molecules that tends to hold them together. Types of bonds include covalent, ionic, and hydrogen.

Antioxidants

Any molecule that reacts with free molecules, neutralizing their ability to damage biological molecules. Vitamins C and E are examples of dietary antioxidants.

Cancer is caused by DNA mutations. What exactly do cigarette smoke and radiation do that can cause cancer? A) Cigarette smoke and radiation both cause damage to DNA, leading to mutation. B) Cigarette smoke and radiation both cause free radicals, which damage DNA, leading to mutations. C) Radiation causes free radicals. Cigarette smoke causes DNA damage. D) Cigarette smoke damages DNA, leading to free radicals. Radiation causes mutations in DNA.

B) Cigarette smoke and radiation both cause free radicals, which damage DNA, leading to mutations.

How do atoms respond when they absorb energy? A) Protons and neutrons leave the nucleus. B) Electrons move to a higher orbital. C) Electrons emit light. D) Neutrons leave the nucleus. E) Electrons vibrate faster. F) The nucleus vibrates.

B) Electrons move to a higher orbital.

Why is the town of Pripyat uninhabited? A) The constant intrusion by reporters keeps people away. B) The radiation levels in the town are still unsafe. C) There is a high risk of another explosion. D) Wildlife has taken over the area, making it unsafe for humans.

B) The radiation levels in the town are still unsafe.

Milk of magnesia is often used to treat stomach upset. It has a pH of 10. Based on this information, milk of magnesia A) has the same pH as stomach acid. B) is a base. C) is hydrophobic. D) is an acid.

B) is a base.

How can an atomwith an almost empty outermost shell become more stable?

By completely emptying out the outermost electron shell

How can an atom with an almost full outermost shell become more stable?

By gaining more electrons and filling the shell completely. *It also becomes negatively charged

How does an atom become positively charged?

By losing electrons

We may never know how many people became ill or died as a result of the Chernobyl accident. What is the main reason why this is so difficult to determine? A) Radiation only affects plants and wildlife (but not humans) because they are outdoors and exposed to more radiation. B) The effects of ionizing radiation on the human body are never visible. C) Cancer might not occur for many years after exposure to ionizing radiation. D) The Ukrainian government did not keep data on births and deaths.

C) Cancer might not occur for many years after exposure to ionizing radiation.

Why is ionizing radiation damaging to cells? A) It causes the cells to melt and bind to one other. B) It causes the molecules within the cells to melt together in a compacted lump. C) It knocks the electrons from the cell's molecules, forming ions and breaking bonds. D) It causes the water in the cells to boil.

C) It knocks the electrons from the cell's molecules, forming ions and breaking bonds.

Why does ice float? A) Solids are less dense in general than their liquid form. B) The hydrogen bonds between molecules of liquid water are stronger than those of the solid, pulling the liquid molecules closer together. C) The hydrogen bonds in solid water force the molecules farther apart from one another than the same bonds in liquid water. D) The energy contained in the hydrogen bonds of ice is greater than the energy contained in the hydrogen bonds of water.

C) The hydrogen bonds in solid water force the molecules farther apart from one another than the same bonds in liquid water.

How does water dissolve salt? A) The oxygen atoms of water form a polar covalent bond with the sodium atom. B) The hydrogen atoms of water form hydrogen bonds with a negatively charged chlorine ion. C) The partial positive charges of the hydrogen atoms on water surround the negative charge of a chlorine ion. D) The positive charges of the oxygen atoms on water balance the partial negative charge of a sodium atom. E) The partial positive charges of hydrogen form covalent bonds with a negatively charged chloride ion.

C) The partial positive charges of the hydrogen atoms on water surround the negative charge of a chlorine ion.

Many of the first responders at the Chernobyl accident died within hours or days of working at the explosion site. What were they most likely to die from, and why? A) cancer due to toxins in the soil B) smoke inhalation from battling the fires on the roof of the reactor building C) acute radiation sickness due to exposure to ionizing radiation D) injuries caused by projectiles from the explosion

C) acute radiation sickness due to exposure to ionizing radiation

The atomic number of hydrogen is 1. Based on this fact, all of the following must be true of hydrogen gas (H2) EXCEPT that it A) shares one pair of electrons between the two hydrogen atoms. B) uses covalent bonds to form the molecule. C) is a polar molecule. D) is a stable molecule.

C) is a polar molecule.

Sweating is a useful cooling mechanism for humans because water _________________ A) takes up a great deal of heat in changing from its solid state to its liquid state. B) is an outstanding solvent. C) takes up a great deal of heat in changing from its liquid state to its gaseous state D) can exist in two states at temperatures common on Earth. E) ionizes readily.

C) takes up a great deal of heat in changing from its liquid state to its gaseous state

Which of the following best explains the attraction of water molecules to each other? A) Nonpolar covalent bond B) Polar covalent bond C) Ionic bond D) Hydrogen bond E) Electron-proton interaction

D) Hydrogen bond

The concrete sarcophagus enclosing the damaged reactor is crumbling, allowing radiation to leak out into the environment. An animation of a new protective cover is shown in the video. Why hasn't the construction of this cover been completed? A) It will not protect against ionizing radiation. B) We do not have the technology or skill to build it. C) The danger for the radioactive materials no longer exists. D) It will be extremely expensive to build.

D) It will be extremely expensive to build.

In addition to the risk of accidents, which of the following is a problem when nuclear power is used as a method of generating electrical power? A) large production of carbon dioxide B) a large amount of gasoline or natural gas is required C) constant release of polluting smog released from the smokestacks D) storage and disposal of spent fuel rods

D) storage and disposal of spent fuel rods

A single covalent chemical bond represents the sharing of how many electrons? A) Six B) One C) Three D) Four E) Two

E) Two

Why is water special when it freezes?

It becomes less dense than when it is a liquid.

Why is the property of water being less dense when it is frozen essential to life?

It is crucial to the distribution of aquatic life. When water freezes, it creates an insulation layer of ice that protects aqudic life from freezing.

What are the roles of Nuclei and electrons in atoms?

Nuclei (unless they are radioactive) provide stability and remain uncharged during ordinary chemical reactions. Electrons, in contrast, remain dynamic; they can capture and release energy and they form the bonds that link atoms togetehr into molecules.

Isotopes

One of several forms of a single element, the nuclei of which contain the same number of protons but different numbers of neutrons

Radioactive

Pertaining to an atom with an unstable nucleus that spontaneously breaks apart or decays, with the emission of radiation. *The decay of radioactive nuclei form new elements *When one decays energy is released and a neutron is converted to a proton, producing a stable nitrogen atom. *Scientists measure levels of carbon to accurately assess the age of artifacts.

Hydrophilic

Pertaining to molecules that dissolve readily in water, or to molecules that form hydrogen bonds with water; polar. *Ex: salt

Hydrophobic

Pertaining to olecules that do not dissolve in water or form hydrogen bonds with water; nonpolar. *Ex: oil

Acidic

Referring to a solution with and H+ concentration exceeding that of OH-; referring to a substance that releases H+.

Basic

Referring to a solution with and H+ concentration less than that of OH-; referring to a substance that combines with H+.

Specific heat

The ammount of energy required to raise the temperature of one gram of a substance by 1 degree celcius.

Atomic nucleus

The central part of an atom that contains protons and neutrons.

Heat of vaporization

The energy that must be supplied to a compound to transform it from a liquid into a gas at its boiling temperature.

Capillary action

The movement of water within narrow spaces among charged surfaces resulting from its properties of cohesion and adhesion. *Ex: a corner of a paper towel is placed in a bowl containing water. Capillary action happens when the water is drawn from the bowl and into the rest of the paper towel

Atomic number

The number of protons in the neuclei of all atoms of a particular element.

Dissolve

The process by which solvent molecules completely surround and disperse the indivisual atoms or molecules of another subance, the solute.

Surface tension

The property of a liquid to resist penetration by objects at its interface with the air, due to cohesion between molecules of the liquid. *Ex: A lizard uses surface tension as it races across the water's surface to escape a predator

Atom

The smallest unit of an element that retains the properties of an element.

Adhesion

The tendancy of polar molecules (such as water) to adhere to polar surfaces (such as glass).

Cohesion

The tendency of the molecules of s substance to stick together. *Ex: Causes water to form droplets

Mass number

The total number of protons and neutrons in the nucleus of an atom.

Predict how a drop of water on an oil coated surface would differ in shape from a clean glass surface.

The water would spread out on a clean glass surface because of adhesion to the glass and cohesion among the water molecues. On an oil covered slide of glass, the water droplet would round up due to hydrophobic interactions.

Hydrogen bonds

The weak attraction between a hydrogen atom that bears a partial positive charge (due to polar covalent bonding with another atom) and another atom ( oxygen, nitrogen, r fluorine) that bears a partial negative charge; hydrogent bonds may form between atoms of a single molecule or of different molecules.

Neutron

a subatomic particle that is found in the nuclei of atoms, bears no charge, and has a mass aproximately equal to that of a proton.

Proton

a subatomic particle that is found in the nuclei of atoms; it bears a unit of positive charge and has a relatively large mass, roughly equal to that of a neutron.

Electron

a subatomic particle, found in an electron shell outside the nucleus of an atom, that bears a unit of negative charge and very little mass.

Subatomic particles are assigned their own unit of mass, are measured in _____________ .

atomic mass units

An atom as a whole is ________________ , or neutral, because it contains equal numbers of protons and electrons, whose positive and negative electrical charges balance each other out.

uncharged