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Questions and Answers
What results from the sharing of six electrons between two atoms?
What results from the sharing of six electrons between two atoms?
What happens to a sodium atom when it loses one electron?
What happens to a sodium atom when it loses one electron?
Which of the following best defines a molecule?
Which of the following best defines a molecule?
How do atoms achieve electrical neutrality in ionic bonds?
How do atoms achieve electrical neutrality in ionic bonds?
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Which type of bond involves electrons traveling about the nuclei of both atoms?
Which type of bond involves electrons traveling about the nuclei of both atoms?
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What is the charge on a chloride ion?
What is the charge on a chloride ion?
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In the context of chemical bonds, what term best describes valence electrons?
In the context of chemical bonds, what term best describes valence electrons?
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What is the primary characteristic of an ionic bond?
What is the primary characteristic of an ionic bond?
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Which property is NOT associated with the compound sodium chloride?
Which property is NOT associated with the compound sodium chloride?
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What is the chemical formula for water?
What is the chemical formula for water?
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Which isotope is used to follow the movements of substances within organisms?
Which isotope is used to follow the movements of substances within organisms?
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Which element is NOT paired correctly with its chemical property?
Which element is NOT paired correctly with its chemical property?
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How do geologists use radioactive isotopes?
How do geologists use radioactive isotopes?
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What combination forms liquid water?
What combination forms liquid water?
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Which use is NOT listed for radioactive isotopes?
Which use is NOT listed for radioactive isotopes?
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Which statement about the physical properties of chemical compounds is accurate?
Which statement about the physical properties of chemical compounds is accurate?
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What defines the chemical properties of an element?
What defines the chemical properties of an element?
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What is the atomic number of an element?
What is the atomic number of an element?
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Which of these statements is correct regarding isotopes?
Which of these statements is correct regarding isotopes?
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What is the mass number of an atom?
What is the mass number of an atom?
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How does the abundance of an isotope in nature affect its atomic mass?
How does the abundance of an isotope in nature affect its atomic mass?
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Which element is NOT commonly found in living organisms?
Which element is NOT commonly found in living organisms?
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Why do different elements have such differing properties?
Why do different elements have such differing properties?
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Which carbon isotope is radioactive?
Which carbon isotope is radioactive?
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Which scientist introduced the concept of the atom nearly 2,500 years ago?
Which scientist introduced the concept of the atom nearly 2,500 years ago?
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How many sulfur atoms placed side-by-side would approximately equal the width of a pinky finger?
How many sulfur atoms placed side-by-side would approximately equal the width of a pinky finger?
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Which subatomic particle has no charge?
Which subatomic particle has no charge?
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Where in the atom do protons and neutrons reside?
Where in the atom do protons and neutrons reside?
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What is the mass of an electron relative to a proton?
What is the mass of an electron relative to a proton?
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How many electrons can the first shell of an atom hold?
How many electrons can the first shell of an atom hold?
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What ensures that atoms are electrically neutral?
What ensures that atoms are electrically neutral?
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Which force binds protons and neutrons together in the nucleus?
Which force binds protons and neutrons together in the nucleus?
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What allows geckos to scurry up walls and across ceilings?
What allows geckos to scurry up walls and across ceilings?
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What is the main function of the weak interactions within a living cell?
What is the main function of the weak interactions within a living cell?
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Which statement BEST describes van der Waals forces?
Which statement BEST describes van der Waals forces?
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What is the composition of the projections on a gecko's feet that assist in van der Waals interactions?
What is the composition of the projections on a gecko's feet that assist in van der Waals interactions?
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Why are hydrogen bonds essential to understanding the special properties of water?
Why are hydrogen bonds essential to understanding the special properties of water?
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What characteristic of molecules enhances the effectiveness of van der Waals forces?
What characteristic of molecules enhances the effectiveness of van der Waals forces?
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What term is used to describe the shared action or influence between molecules?
What term is used to describe the shared action or influence between molecules?
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Which atoms in a neighboring molecule can form hydrogen bonds with a hydrogen atom?
Which atoms in a neighboring molecule can form hydrogen bonds with a hydrogen atom?
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Study Notes
Elements and Isotopes
- A chemical element is a pure substance that consists entirely of one type of atom.
- Elements are represented by one or two-letter symbols.
- The number of protons in the nucleus of an element is called its atomic number.
- Carbon's atomic number is 6, meaning that each atom of carbon has six protons and six electrons.
- Nearly 100 naturally occurring chemical elements exist on Earth, but fewer than 20 are commonly found in living organisms.
- About 99% of the mass of living things is composed of just six elements: calcium, carbon, hydrogen, oxygen, nitrogen, and phosphorus.
- The remaining 1% of elements are also essential and are known as trace elements.
Isotopes
- Atoms of an element may have different numbers of neutrons.
- Atoms of the same element that differ in the number of neutrons they contain are known as isotopes.
- The total number of protons and neutrons in the nucleus of an atom is called its mass number.
- Isotopes are identified by their mass numbers.
- The weighted average of the masses of an element's isotopes is called its atomic mass.
- Neutrons affect the atomic mass of an isotope but do not affect its chemical properties.
Radioactive Isotopes
- Radioactive isotopes are unstable and break down at a constant rate over time.
- Radioactive isotopes have important scientific and practical uses, such as:
- Determining the ages of rocks and fossils
- Detecting cancer and killing bacteria that cause food to spoil
- Using as labels or "tracers" to follow the movements of substances within organisms
Chemical Compounds
- A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions.
- Scientists show the composition of compounds by a kind of short-hand known as a chemical formula.
- The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed.
Chemical Bonds
- The atoms in compounds are held together by chemical bonds.
- The main types of chemical bonds are:
- Ionic bonds: formed when one or more electrons are transferred from one atom to another
- Covalent bonds: formed when electrons are shared between atoms
- Bond formation involves the electrons that surround each atomic nucleus.
Weak Interactions
- Weak interactions between atoms and molecules are important in living things.
- Examples of weak interactions include:
- Van der Waals forces: a slight attraction between molecules when they are very close together
- Hydrogen bonds: form between a hydrogen atom of one molecule and an oxygen or nitrogen atom of a neighboring molecule
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Description
Learn about the basics of chemical elements, their symbols, atomic numbers, and the structure of atoms. Understand the concept of isotopes and how they differ from elements.
