Question

Which of the following statements about molecules is true? a. A single molecule contains atoms from only one element. b. Atoms in a molecule are linked only via ionic bonds. c. Molecules are found only in living organisms. d. Molecules can contain as few as two atoms.

Short answer

Statement D is true.

Step-by-step solution

Analyze Statement A

Evaluate if a single molecule contains atoms from only one element. Examples such as water (H2O) and carbon dioxide (CO2) contain more than one element. Therefore, statement A is false.

Analyze Statement B

Consider if atoms in a molecule are linked only via ionic bonds. Molecules also have covalent bonds, like in H2O, where hydrogen and oxygen atoms are bonded covalently. Hence, statement B is false.

Analyze Statement C

Determine if molecules are found only in living organisms. Molecules are present in non-living matter as well, such as oxygen (O2) and nitrogen (N2) in the atmosphere. Therefore, statement C is false.

Analyze Statement D

Check if molecules can contain as few as two atoms. Diatomic molecules like oxygen (O2) and hydrogen (H2) have only two atoms. Hence, statement D is true.

Key concepts

Chemical Bonds

Chemical bonds are the forces that hold atoms together in molecules. They are essential for the formation of compounds and the stability of substances. There are two main types of chemical bonds: ionic bonds and covalent bonds.

• Ionic bonds: These bonds form when one atom transfers electrons to another atom, resulting in positive and negative ions that attract each other.
• Covalent bonds: These bonds form when atoms share one or more pairs of electrons to achieve a full outer shell.

Understanding chemical bonds is crucial for explaining why substances have different properties, such as melting points, boiling points, and electrical conductivity.

Elements

Elements are pure substances made up of only one kind of atom. Each element is defined by the number of protons in its nucleus, known as the atomic number. For example, hydrogen has one proton, while oxygen has eight protons. Elements are the building blocks of all matter and can combine in various ways to form compounds.

Some key points about elements include:

• There are 118 known elements, each with its unique properties.
• Elements are arranged in the periodic table based on their atomic number and chemical properties.
• Some elements, like gold and silver, are found in their pure form in nature, while others, like sodium and chlorine, are usually found in compounds.

Covalent Bonds

Covalent bonds are a type of chemical bond where two atoms share one or more pairs of electrons. This sharing allows each atom to achieve a stable electron configuration, similar to that of noble gases. Covalent bonds can form between atoms of the same element or different elements.

• Single covalent bonds: Involve one pair of shared electrons, like in hydrogen gas (H2).
• Double covalent bonds: Involve two pairs of shared electrons, like in oxygen gas (O2).
• Triple covalent bonds: Involve three pairs of shared electrons, like in nitrogen gas (N2).

Molecules with covalent bonds often have lower melting and boiling points compared to those with ionic bonds and can exist as gases, liquids, or solids at room temperature.

Diatomic Molecules

Diatomic molecules are molecules composed of only two atoms. These can be two atoms of the same element or two different elements. Diatomic molecules are important in chemistry and are often found in nature.

Examples include:

• Hydrogen (H2): The simplest diatomic molecule, consisting of two hydrogen atoms sharing a single covalent bond.
• Oxygen (O2): Essential for respiration in most organisms, it consists of two oxygen atoms sharing a double covalent bond.
• Nitrogen (N2): Makes up about 78% of the Earth's atmosphere, with two nitrogen atoms sharing a triple covalent bond.
• Chlorine (Cl2): Commonly used in disinfection and bleaching, consisting of two chlorine atoms with a single covalent bond.

Recognizing diatomic molecules helps in understanding chemical reactions and properties of elements, especially in gases.