chapter 2 biology

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Questions and Answers

What is the charge of neutrons in a carbon atom?

Variable charge

Positive charge

Negative charge

No charge (correct)

Where are electrons located within a carbon atom?

Embedded within neutrons

Within the protons

In regions outside the nucleus called orbitals (correct)

In the nucleus only

What is the total number of subatomic particles in a neutral carbon atom?

12 (correct)

What primarily holds an atom together?

The attractions between protons and electrons Signup and view all the answers

What is the atomic mass unit (amu) of protons and neutrons in a carbon atom?

1 amu for both Signup and view all the answers

What does the atomic number represent for an element?

The number of protons in an atom Signup and view all the answers

What is the definition of mass number?

The total number of protons and neutrons in an atom Signup and view all the answers

Why are radioactive isotopes considered useful in research?

They act as effective tracers for monitoring atom movement Signup and view all the answers

What does a full outer electron shell indicate about an atom's reactivity?

It is relatively stable and less likely to interact Signup and view all the answers

What determines an atom's chemical properties?

The arrangement of electrons in its shells Signup and view all the answers

How do chemical bonds form between atoms?

By sharing, gaining, or losing electrons Signup and view all the answers

What effect does a partial outer electron shell have on an atom?

It leads to the atom's ability to bond with others Signup and view all the answers

Which of the following statements about isotopes is true?

Isotopes differ in their neutron count Signup and view all the answers

What happens when carbon dioxide (CO2) dissolves in water?

It reacts to form an acid that disrupts coral skeletons. Signup and view all the answers

Which of the following statements about living organisms is correct?

About 25 essential elements are required to sustain human life. Signup and view all the answers

What is the role of trace elements in food and water?

They prevent diseases and improve food quality. Signup and view all the answers

How does table salt exemplify the concept of emergent properties?

It combines two different elements to create a compound with unique properties. Signup and view all the answers

What is a consequence of ingesting more than the tolerable upper intake level of iron?

It may lead to gastrointestinal upset. Signup and view all the answers

Why might fluoride be added to municipal water?

To help reduce tooth decay. Signup and view all the answers

What constitutes a compound?

A substance consisting of two or more different elements in a fixed ratio. Signup and view all the answers

What is the primary distinction between ionic and covalent bonds?

Ionic bonds result from the transfer of electrons, whereas covalent bonds result from the sharing of electrons. Signup and view all the answers

In a polar covalent bond, what causes the unequal sharing of electrons?

The differences in electronegativity between the atoms. Signup and view all the answers

Which of the following best describes an ion?

A charged atom or molecule resulting from the loss or gain of electrons. Signup and view all the answers

What characterizes a nonpolar covalent bond?

Electrons are shared equally between the atoms. Signup and view all the answers

What term is used to describe the attraction between ions of opposite charges?

Ionic bond Signup and view all the answers

Which molecule typically exhibits polar covalent bonds due to its structure?

Water (H₂O) Signup and view all the answers

Which statement about ionic compounds is true?

Ionic compounds typically form through the combination of metals with nonmetals. Signup and view all the answers

What results from the interaction of two ions with opposite charges?

Formation of an ionic bond Signup and view all the answers

What is the role of buffers in a solution?

They minimize changes in pH. Signup and view all the answers

What is the primary consequence of rising atmospheric CO2 on oceanic pH levels?

It causes ocean acidification, lowering pH levels. Signup and view all the answers

What happens to carbonate ions in seawater as acidity increases?

They react with hydrogen ions to form bicarbonate ions. Signup and view all the answers

How does ocean acidification directly affect reef organisms?

It reduces available carbonate ions needed for shell-building. Signup and view all the answers

What aspect of climate change is primarily linked to the rise in atmospheric CO2?

Global warming and its ecological impacts. Signup and view all the answers

In the context of water chemistry, what occurs when water molecules break apart?

It produces both hydrogen ions and hydroxide ions. Signup and view all the answers

What is the outcome of scientists studying the effects of decreasing carbonate ion concentrations?

They evaluated the impact on the rate of calcium deposition in coral. Signup and view all the answers

Which ion is produced when CO2 is absorbed by seawater and causes a decrease in pH?

Hydrogen ion (H+) Signup and view all the answers

How does the concentration of carbonate ions relate to coral calcification rates?

Higher carbonate ion concentration increases calcification rates. Signup and view all the answers

What is the primary impact of rising atmospheric CO2 on coral reefs?

It leads to ocean acidification, reducing carbonate ion availability. Signup and view all the answers

Which property of water is crucial for the emergence of life on other planets?

Its polar nature facilitates nutrient transport and chemical reactions. Signup and view all the answers

Which of the following best describes a characteristic of coral calcification?

It requires a stable pH level for optimal rates. Signup and view all the answers

What is the role of chemical reactions in living organisms?

They alter the composition of matter to support metabolic functions. Signup and view all the answers

Why is pH control significant in marine ecosystems?

It affects the solubility of gases in ocean water. Signup and view all the answers

How does ocean acidification primarily affect coral reefs?

It decreases the availability of carbonate ions needed for calcification. Signup and view all the answers

Which statement accurately describes the relationship between water and life on Earth?

Water's unique properties allow it to directly support biological processes. Signup and view all the answers

Study Notes

Chapter 2: The Chemical Basis of Life

The chemical composition of the air can harm coral reefs
When carbon dioxide dissolves in water, it reacts with water to produce an acid
This acid can disrupt the formation of coral skeletons

Elements, Atoms, and Compounds

Living organisms are composed of matter
Matter is made of chemical elements
Approximately 25 elements are essential for human life
Four elements (oxygen, carbon, hydrogen, and nitrogen) make up about 96% of the weight of most living organisms
A compound is a substance consisting of two or more different elements in a fixed ratio

Atoms Consist of Protons, Neutrons, and Electrons

Each element consists of one kind of atom
An atom is the smallest unit of matter with the properties of an element
Neutrons and protons are packed into the nucleus of an atom
Electrons orbit the nucleus
The unique number of protons is an element's atomic number
An atom's mass number is the sum of its protons and neutrons in the nucleus
The atomic mass is approximately equal to its mass number
Isotopes of an element have the same number of protons, but different numbers of neutrons
Molecules are two or more atoms combined
Compounds are a defined number of atoms in a defined spatial relationship (combination of elements with a defined ratio)

Valence Electrons

Atoms whose shells are not full tend to interact with other atoms to gain, lose, or share electrons
Valence electrons are the number of electrons in the outer shell of an atom
The outermost electron shell can hold 8 electrons
The first electron shell can hold 2 electrons

Periodic Table

The periodic table lists all known elements
Elements with no stable isotopes have mass numbers in parentheses.

2.4 Connection: Radioactive Isotopes Can Help or Harm Us

Radioactive isotopes are useful as tracers for monitoring the fate of atoms in living organisms
Sophisticated imaging instruments can detect radioactive isotopes
There are also dangers associated with using radioactive substances

Water's Life-Supporting Properties

Water is less dense as a solid than a liquid, due to hydrogen bonding
When water freezes, each molecule forms a stable hydrogen bond with its neighbors
As ice crystals form, the molecules are less densely packed than in liquid water
Ice floats because it is less dense than water

2.13 Water is the Solvent of Life

A solution is a liquid consisting of a uniform mixture of two or more substances
Water's versatility as a solvent results from the polarity of its molecules
Polar or charged solutes dissolve when water molecules surround them, forming aqueous solutions

2.14 The Chemistry of Life Is Sensitive to Acidic and Basic Conditions

In liquid water, a very small percentage of water molecules break apart into ions (H⁺ and OH⁻)
The pH scale is used to describe how acidic or basic a solution is
A buffer minimizes changes in pH

2.15 Scientific Thinking: Scientists Study the Effects of Rising Atmospheric CO2 on Coral Reef Ecosystems

Carbon dioxide is the main product of fossil fuel combustion, increasing in the atmosphere, and linked to global climate change
Approximately 25% of this human-generated CO2 is absorbed by the vast oceans
CO2 dissolved in seawater lowers the pH of the ocean in a process known as ocean acidification
As seawater acidifies, the extra hydrogen ions (H⁺) combine with carbonate ions (CO₃²⁻) to form bicarbonate ions (HCO₃⁻)
This reaction reduces the carbonate ion concentration available to corals and other shell-building animals

2.16 Evolution Connection: The Search for Extraterrestrial Life Centers on the Search for Water

The emergent properties of water support life on Earth and may contribute to the potential for life to have evolved on other planets

You Should Now Be Able To

Describe the importance of chemical elements to living organisms
Explain the formation of compounds
Describe the structure of an atom
Distinguish between ionic, hydrogen, and covalent bonds
Define a chemical reaction and explain how it changes the composition of matter
List and define the life-supporting properties of water
Explain the pH scale and the formation of acid and base solutions
Explain how rising CO2 levels affect coral reefs

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Test your knowledge on atomic structure with this quiz, covering key concepts related to carbon atoms and subatomic particles. Explore topics such as electron arrangement, atomic mass, and the role of isotopes in research. Perfect for students learning chemistry fundamentals.