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Questions and Answers
What is the shape of the methane molecule (CH4) due to its bond arrangement?
What is the shape of the methane molecule (CH4) due to its bond arrangement?
What characteristic defines a polar covalent bond?
What characteristic defines a polar covalent bond?
How does electronegativity influence the behavior of atoms in a molecule?
How does electronegativity influence the behavior of atoms in a molecule?
Which of the following scenarios would result in a non-polar covalent bond?
Which of the following scenarios would result in a non-polar covalent bond?
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What is the electronegativity difference that identifies an ionic bond?
What is the electronegativity difference that identifies an ionic bond?
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What is the maximum number of electrons that the third shell can hold?
What is the maximum number of electrons that the third shell can hold?
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What primarily composes organic compounds that make up 96% of the weight of a living organism?
What primarily composes organic compounds that make up 96% of the weight of a living organism?
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Which subatomic particle is responsible for determining the identity of an atom?
Which subatomic particle is responsible for determining the identity of an atom?
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Which of the following statements about the 1s shell is true?
Which of the following statements about the 1s shell is true?
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What type of bond is formed by the attraction between a cation and an anion?
What type of bond is formed by the attraction between a cation and an anion?
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What defines an isotope of an element?
What defines an isotope of an element?
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In beta decay of 14C, what does one neutron transform into?
In beta decay of 14C, what does one neutron transform into?
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Which type of atom is most likely to lose electrons?
Which type of atom is most likely to lose electrons?
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What does the term electronegativity refer to?
What does the term electronegativity refer to?
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What is the half-life of 14C, used in dating fossils?
What is the half-life of 14C, used in dating fossils?
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Which statement about electrons is false?
Which statement about electrons is false?
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What is the first shell called and how many electrons does it hold?
What is the first shell called and how many electrons does it hold?
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Which element is produced as a result of the decay of 14C?
Which element is produced as a result of the decay of 14C?
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What happens to atoms that are nonmetals in terms of electrons?
What happens to atoms that are nonmetals in terms of electrons?
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Which of the following describes the shape of the 2p orbital?
Which of the following describes the shape of the 2p orbital?
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What factor is used to determine the age of fossils when measuring the ratio of 14C to 12C?
What factor is used to determine the age of fossils when measuring the ratio of 14C to 12C?
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Study Notes
Fundamental Chemistry of Life
- Matter comprises everything in the universe, including living organisms.
- Element: A pure substance that cannot be broken down.
- Atom: The smallest particle of an element.
- Atoms combine in ratios to create molecules and compounds.
Organic Compounds
- Organic compounds are primarily made of carbon (C), hydrogen (H), oxygen (O), and sometimes nitrogen (N).
- Organic compounds make up 96% of the weight of a living organism.
- Other elements like calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl), and magnesium (Mg) account for the remaining 4%.
Differences between Living and Non-living Things
- Similar elements are present in various living and non-living organisms but in different ratios.
- Living organisms have significantly higher proportions of oxygen, carbon, hydrogen, and nitrogen compared to non-living examples like seawater, pumpkins or the earth's crust.
Atomic Structure
- Atoms consist of protons, neutrons, and electrons.
- Protons define an atom's identity.
- Atomic mass equals the sum of protons and neutrons.
Subatomic Particle Summary
- Protons: Positively charged, located in the nucleus, and equal to the atomic number.
- Neutrons: Neutral charge, located in the nucleus, and calculated by subtracting the atomic number from the atomic mass.
- Electrons: Negatively charged, found in outer orbitals, and equal to the atomic number.
Isotopes and Radioisotopes
- Isotopes: Atoms of the same element with the same number of protons but different numbers of neutrons.
- Radioisotopes: Unstable isotopes that decay and emit particles, detectable as radioactivity.
- Isotopes of the same element behave identically in chemical reactions.
Radioisotopes
- Radioisotopes decay, transforming into a more stable atom of a different element.
- The decay process produces detectable radioactive signals.
In Beta Decay
- A neutron in an unstable isotope turns into a proton.
- This results in a new element forming.
Carbon-14 Dating
- The ratio of Carbon-14 to Carbon-12 is constant in living things (1:1x1012).
- In fossils, the Carbon-14 ratio decreases over time, allowing scientists to determine the age of the organism since death.
- The half-life of Carbon-14 is 5730 years.
Electron Arrangements in Orbitals
- Electrons are equal to protons (neutral atoms).
- Electrons occupy orbitals (shells).
- Shells are numbered (1, 2, 3...).
- The first shell holds 2 electrons, the second 8, and the third 18.
- Shells use s, p, d, f orbitals.
Electron Shells
- The first shell (1s) is spherical and holds two electrons.
- The second shell (2s) is spherical and larger than the first and holds two electrons.
- The second shell also contains three 2p orbitals, each holding two electrons for a total of six.
Valence Electrons
- Valence electrons are the outermost shell electrons.
- Atoms with unfilled outer shells are reactive.
- Valence electrons are used in Lewis dot diagrams to illustrate bonding.
Giving, Taking, and Sharing
- Atoms with few outer electrons tend to lose them, becoming positive ions (cations).
- Atoms with many outer electrons tend to gain more to become negative ions (anions).
- Atoms share electrons to complete outer shells, forming covalent bonds.
Chemical Bonds in Biological Molecules
- Ionic bonds form due to attraction between oppositely charged ions.
- Covalent bonds form when atoms share pairs of valence electrons, forming molecules with a distinct structure.
- Electronegativity measures an atom's attraction for electrons, influencing covalent bond strength and polarity.
Chemical Bonds in Biological Molecules (continued)
- Covalent bonds determine the structure of molecules.
- An example, carbon (C) forms four covalent bonds, making complex molecules possible.
Polar Molecules
- Polarity is a property of molecules.
- Electronegativity influences polarity, with higher electronegativity values attracting electrons more strongly.
- Unequal sharing of electrons between atoms creates partial charges in molecules.
- Polarity affects solubility and interactions with other molecules.
Determining Polarity
- Bonds between different atoms are often polar.
- The difference in electronegativity between two atoms measures its polarity, with large differences indicating more ionic bonds and smaller indicating covalent bonds.
- Nonpolar molecules have no net charge.
Properties of Polar Molecules
- Polar molecules tend to dissolve in other polar substances but not in non-polar ones.
- Water is a powerful polar solvent.
Intermolecular Forces
- Intermolecular forces are attractions between different molecules.
- Van der Waals, hydrogen bonds, and dipole-dipole interactions affect interactions between molecules.
Intermolecular Forces (continued)
- Van der Waals forces are weaker than covalent bonds.
- Hydrogen bonds, a special type of dipole-dipole interaction, are particularly strong from the positive hydrogen and negative oxygen attraction and are prevalent in biological molecules.
Hydrogen Bonds and Biological Significance
- Hydrogen bonds are relatively weak, but significant in large numbers.
- Hydrogen bonding stabilizes the complex shapes of biological molecules like proteins.
Chemical Reactions
- Dehydration synthesis: Removing water to link subunits.
- Hydrolysis: Adding water to break down molecules.
Neutralization Reactions
- A reaction between an acid and a base that produces a salt and water.
Redox Reactions
- Oxidation: Loss of electrons.
- Reduction: Gain of electrons.
Homework
- Use radioisotope decay for diagnosing thyroid issues using radioactive iodine-131.
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Description
Explore the basics of chemistry that underlie all living organisms. This quiz covers key concepts such as matter, organic compounds, and the distinctions between living and non-living things. Test your understanding of atomic structure and the elements essential to life.
