40 Questions
What results from the sharing of six electrons between two atoms?
A molecule with a triple covalent bond
What happens to a sodium atom when it loses one electron?
It becomes a sodium ion with a positive charge
Which of the following best defines a molecule?
The smallest unit of most compounds formed by covalent bonds
How do atoms achieve electrical neutrality in ionic bonds?
By transferring electrons to form ions
Which type of bond involves electrons traveling about the nuclei of both atoms?
Covalent bond
What is the charge on a chloride ion?
Negative
In the context of chemical bonds, what term best describes valence electrons?
Electrons available for bond formation
What is the primary characteristic of an ionic bond?
Electrons are transferred from one atom to another
Which property is NOT associated with the compound sodium chloride?
Poisonous yellow-green gas
What is the chemical formula for water?
H2O
Which isotope is used to follow the movements of substances within organisms?
Iodine-131
Which element is NOT paired correctly with its chemical property?
Chlorine - unreactive
How do geologists use radioactive isotopes?
To determine the ages of rocks and fossils
What combination forms liquid water?
Hydrogen and oxygen
Which use is NOT listed for radioactive isotopes?
Increasing animal reproduction rates
Which statement about the physical properties of chemical compounds is accurate?
They are usually very different from the properties of the elements from which they are formed.
What defines the chemical properties of an element?
The number of electrons in the outer shell
What is the atomic number of an element?
The number of protons in the nucleus
Which of these statements is correct regarding isotopes?
Isotopes of an element have the same number of protons but different numbers of neutrons.
What is the mass number of an atom?
The total number of protons and neutrons in the nucleus
How does the abundance of an isotope in nature affect its atomic mass?
It contributes to the weighted average of the atomic mass
Which element is NOT commonly found in living organisms?
Iodine
Why do different elements have such differing properties?
Due to different arrangements and interactions of electrons in their shells
Which carbon isotope is radioactive?
Carbon-14
Which scientist introduced the concept of the atom nearly 2,500 years ago?
Democritus
How many sulfur atoms placed side-by-side would approximately equal the width of a pinky finger?
100,000,000
Which subatomic particle has no charge?
Neutron
Where in the atom do protons and neutrons reside?
Nucleus
What is the mass of an electron relative to a proton?
1/1840
How many electrons can the first shell of an atom hold?
2
What ensures that atoms are electrically neutral?
Equal number of protons and electrons
Which force binds protons and neutrons together in the nucleus?
Strong nuclear force
What allows geckos to scurry up walls and across ceilings?
Millions of tiny hairlike projections on their feet
What is the main function of the weak interactions within a living cell?
To send signals and carry out temporary chemical reactions
Which statement BEST describes van der Waals forces?
They produce a slight attraction between molecules in close proximity.
What is the composition of the projections on a gecko's feet that assist in van der Waals interactions?
Finer fibers
Why are hydrogen bonds essential to understanding the special properties of water?
They form between molecules, affecting water's properties.
What characteristic of molecules enhances the effectiveness of van der Waals forces?
Shapes that match closely with very little space between them
What term is used to describe the shared action or influence between molecules?
Interaction
Which atoms in a neighboring molecule can form hydrogen bonds with a hydrogen atom?
Oxygen or nitrogen atoms
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
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.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
