3.13
Ions, Molecules, and Compounds
Ions - When an atom participates in a chemical reaction that results in the donation or acceptance of one or more electrons, the atom becomes positive…
Ions are electrically charged atoms that have gained or lost electrons. An atom that loses electrons and becomes positively charged is a cation, while an atom that gains electrons and becomes negatively charged is an anion.
Ions are vital to many physiological processes, such as the transmission of nerve impulses and muscle contraction.
Molecules are combinations of two or more atoms that share electrons. They may consist of atoms of one element, like a molecule of oxygen, or atoms of different elements, like a water molecule.
A compound is a combination of atoms of different elements chemically bonded in a fixed proportion, regardless of whether electrons are transferred or shared.
Ionic compounds are formed by electrostatic interaction between metallic and nonmetallic ions, as in ordinary table salt, with a sodium cation and a chloride anion bonded together via electrostatic interactions.
Molecular compounds are formed when nonmetal atoms are bonded via covalent bonds. For example, methane is a molecular compound where four hydrogen atoms share electrons with a carbon atom in a specific proportion.
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Q1: What is the difference between a cation and an anion?
A cation is an atom that has lost electrons and becomes positively charged, while an anion is an atom that has gained electrons and becomes negatively charged. Both form when atoms participate in chemical reactions to achieve a full valence shell. For example, potassium loses one electron to become a cation, and fluorine gains one electron to become an anion.
Q2: Why are ions important to the human body?
Ions are vital to physiological processes including nerve impulse transmission and muscle contraction. Ion imbalances can cause serious health problems: sodium ion imbalance may lead to cardiovascular disease, while low blood calcium levels can cause tetany, which involves uncontrollable involuntary muscle contractions. Maintaining proper ion balance is essential for normal body function.
Q3: How do molecules differ from compounds?
Molecules are combinations of two or more atoms chemically bonded together and may consist of atoms of the same element, like oxygen gas, or different elements, like carbon dioxide. Compounds are pure substances formed by bonding atoms of different elements in a fixed proportion. All compounds are molecules, but not all molecules are compounds.
Q4: What makes ionic compounds different from molecular compounds?
Ionic compounds form through electrostatic interactions between metallic and nonmetallic ions, such as sodium and chloride in table salt. Molecular compounds form when nonmetal atoms bond via covalent bonds, where electrons are shared. In ionic compounds, electrons are transferred; in molecular compounds like methane, electrons are shared between atoms in specific proportions.
Q5: How does an atom become an ion?
An atom becomes an ion when it gains or loses electrons during a chemical reaction, typically to achieve a full valence shell. An atom with a half-full or less-than-half-full valence shell tends to donate electrons, while an atom with a more-than-half-full valence shell tends to accept electrons. This electron transfer results in a net electrical charge on the atom.
Q6: What is the composition of glucose as a compound?
Glucose is a compound composed of three elements—carbon, hydrogen, and oxygen—in a fixed proportion. It always contains six carbon atoms and six oxygen atoms for every twelve hydrogen atoms. This consistent composition makes glucose an important body fuel and demonstrates how compounds maintain specific elemental ratios regardless of their source.
Q7: Why do potassium and fluorine readily participate in chemical reactions?
Potassium has only one electron in its valence shell, making it highly likely to donate that electron to achieve a full shell. Fluorine has seven electrons in its valence shell, making it highly likely to accept one electron to complete its shell. Both elements' electron configurations drive them to participate in chemical reactions to reach stable, full valence shells.