Exam 1 Study Guide: The Chemical Context of Life, Water and Life, Carbon and Molecular Diversity

Flashcards covering atomic structure, chemical bonds, water properties, molarity, pH, carbon versatility, isomers, functional groups, and ATP.

What are the charge, location, relative mass, and role of a proton?

A proton has a charge of $+1$, is located in the nucleus, has a relative mass of $\sim 1\,\text{amu}$, and determines the atomic number / identity of the element.

What are the charge, location, relative mass, and role of a neutron?

A neutron has a charge of $0$, is located in the nucleus, has a relative mass of $\sim 1\,\text{amu}$, and determines the isotope of the element.

What are the charge, location, relative mass, and role of an electron?

An electron has a charge of $-1$, is located in the electron cloud, has a relative mass of $\sim 0\,\text{amu}$, and determines reactivity / chemical behavior.

How do changes in protons, neutrons, and electrons affect an atom?

Changing the number of protons changes the element; changing neutrons changes the isotope; changing electrons changes the charge and chemical reactivity.

How are atomic number and mass number defined?

Atomic number equals the number of protons. Mass number equals the number of protons plus neutrons.

What are cations and anions?

A cation is a positively charged ion formed when an atom loses electrons. An anion is a negatively charged ion formed when an atom gains electrons.

How many protons and electrons does a neutral atom with an atomic number of 8 have?

It has 8 protons and 8 electrons.

If an atom has a mass number of 23 and 11 protons, how many neutrons does it have?

It has 12 neutrons ($23 - 11 = 12$).

Why are electrons generally excluded when calculating an atom's mass number?

Because an electron's mass is negligible / extremely small compared to protons and neutrons.

How do Element X-12 and Element X-14 compare in terms of protons, neutrons, atomic number, and mass number?

Both have the same number of protons and the same atomic number. Element X-12 has 12 neutrons and a mass number of 12, whereas Element X-14 has 14 neutrons and a mass number of 14.

How is net charge calculated for an ion?

Net charge is calculated by subtracting the number of electrons from the number of protons ($\text{protons} - \text{electrons}$).

For an atom with an electron arrangement of 2,8,7, how many total electrons, electron shells, and valence electrons does it have?

It has 17 total electrons, 3 electron shells, and 7 valence electrons.

What does an electron arrangement of 2,8,8 represent?

It represents a full outer shell (8 valence electrons).

What are the valence electrons and outer-shell descriptions for electron arrangements 2,1 and 2,8,2?

2,1 has 1 valence electron (one electron in outer shell); 2,8,2 has 2 valence electrons (two electrons in outer shell).

What are the valence electrons and outer-shell descriptions for electron arrangements 2,8,5 and 2,8,8?

2,8,5 has 5 valence electrons (five electrons in outer shell); 2,8,8 has 8 valence electrons (full outer shell).

What is the key difference between ionic bonds and covalent bonds?

Ionic bonds involve the transfer of electrons and attraction between oppositely charged ions, whereas covalent bonds involve the sharing of electrons.

How many shared electron pairs are in single, double, and triple covalent bonds?

A single covalent bond has one shared pair, a double bond has two shared pairs, and a triple bond has three shared pairs.

What is electronegativity, and how does it affect covalent bond polarity?

Electronegativity is an atom's tendency to attract shared electrons. In polar covalent bonds, electrons are shared unequally; in nonpolar covalent bonds, electrons are shared equally.

What do the symbols $\delta-$ and $\delta+$ indicate in a polar molecule?

$\delta-$ indicates a partial negative charge, and $\delta+$ indicates a partial positive charge.

What is a hydrogen bond?

A hydrogen bond is an attraction between a partially positive hydrogen atom ($\delta+$) and an electronegative atom with a partial negative charge ($\delta-$).

What occurs when a chemical reaction reaches chemical equilibrium?

At chemical equilibrium, the forward and reverse reactions continue but occur at equal rates.

Why is water considered a polar molecule?

Water is polar because oxygen is more electronegative than hydrogen, giving oxygen a partial negative charge ($\delta-$) and hydrogen a partial positive charge ($\delta+$), resulting in uneven charge distribution.

What is the difference between cohesion and adhesion?

Cohesion is the attraction between molecules of the same substance, while adhesion is the attraction between molecules of different substances.

What properties of water result from hydrogen bonding and cohesion?

High surface tension and high specific heat, which allows water to absorb substantial heat energy before its temperature changes rapidly.

Why does ice float on liquid water?

Ice floats because solid water (ice) is less dense than liquid water.

How do nonpolar and polar/charged substances behave in water?

Nonpolar substances are hydrophobic and interact poorly with water; polar or charged substances are hydrophilic and dissolve or interact well with water.

What is the likely behavior in water for hydrocarbons, sugars, ions, methyl groups, and hydroxyl groups?

Hydrocarbon: hydrophobic; Sugar: hydrophilic; Ion: hydrophilic; Methyl group: hydrophobic; Hydroxyl group: hydrophilic.

How does water dissolve ionic compounds?

Water is polar, so its molecules surround dissolved ions through electrostatic / charge-based interactions as the crystal dissociates into individual ions.

What is the formula for molarity (M) and how do you calculate moles from it?

Molarity $(M) = \frac{\text{moles of solute}}{\text{liters of solution}}$. Moles can be calculated using $\text{moles} = \text{molarity} \times \text{volume in liters}$.

What are the three steps to prepare a chemical solution in grams?

1. Determine the desired number of moles. 2. Determine the compound's molar mass. 3. Convert moles into grams.

How do acidic, neutral, and basic solutions compare in their relative concentrations of $H_3O^+$ and $OH^-$?

Acidic: high $H_3O^+$ and low $OH^-$; Neutral: equal $H_3O^+$ and $OH^-$; Basic: low $H_3O^+$ and high $OH^-$.

What is the formula for pH, and what pH ranges designate acidic, neutral, and basic solutions?

$\text{pH} = -\log([H_3O^+])$. Solutions with pH below 7 are acidic, pH equal to 7 are neutral, and pH above 7 are basic.

How much does $H_3O^+$ concentration change with a 1-unit, 2-unit, and 3-unit change in pH?

A 1-unit change represents a factor of 10. pH 3 has 100 times ($10^2$) more $H_3O^+$ than pH 5; pH 4 has 1000 times ($10^3$) more $H_3O^+$ than pH 7.

What happens to $OH^-$ concentration and pH when $H_3O^+$ concentration increases or decreases?

If $H_3O^+$ increases, $OH^-$ decreases and pH decreases. If $H_3O^+$ decreases, $OH^-$ increases and pH increases.

What structural characteristics make carbon chemically versatile?

Carbon has a valence of 4 and can form up to four covalent bonds, including single, double, and triple bonds.

What is a hydrocarbon and what are its general solubility properties?

A hydrocarbon is a molecule composed primarily of carbon and hydrogen; it is nonpolar and hydrophobic.

What are structural isomers, cis-trans isomers, and enantiomers?

Structural isomers differ in the covalent arrangement of atoms; cis-trans isomers result from restricted rotation around a double bond; enantiomers are non-superimposable mirror-image molecules.

What is a chiral center?

A chiral center is an atom (typically carbon) attached to four different chemical groups.

What are the chemical symbols and characteristics for the Hydroxyl, Carbonyl, Carboxyl, Amino, Sulfhydryl, and Methyl functional groups?

Hydroxyl ($-OH$): Water soluble; Carbonyl ($C=O$): Water soluble; Carboxyl ($-COOH$): Acid; Amino ($-NH_2$): Base; Sulfhydryl ($-SH$): Protein structure; Methyl ($-CH_3$): Hydrophobic.

How are acids and bases defined in terms of proton movement?

An acid donates a proton ($H^+$), while a base accepts a proton ($H^+$).

How do ATP and ADP differ in structure and function?

ATP contains adenine, ribose, and three phosphate groups, while ADP contains two phosphate groups. Hydrolysis of ATP into ADP and inorganic phosphate ($P_i$) releases energy for cellular energy transfer.