Isotopes and Electron Configuration

Study Notes

Isotopes

Isotopes are variants of elements with the same number of protons but different numbers of neutrons.
Naturally occurring isotopes include carbon, potassium, and uranium.
Carbon-12 has six protons and six neutrons (mass number 12), with an atomic number of 6.
Carbon-14 has six protons and eight neutrons (mass number 14), also with an atomic number of 6.
Some isotopes are radioactive, meaning they decay to form stable elements over time.
Half-life is the time it takes for half of an isotope's starting concentration to decay; carbon-14 has a half-life of approximately 5,730 years.
Carbon dating uses the ratio of carbon-14 concentration in fossils to atmospheric carbon-14 to estimate ages up to 50,000 years.
Isotopes with longer half-lives, such as potassium-40, can date older fossils.

Electron Configuration and Chemical Bonding

Electron arrangements affect how elements interact; electrons are distributed in energy levels or shells around the nucleus.
The first shell holds up to 2 electrons; subsequent shells hold up to 8 electrons.
The octet rule states atoms seek to fill their outermost shells for stability, leading to the formation of chemical bonds.
Atoms may donate, accept, or share electrons to satisfy the octet rule.
Ions are formed when the number of protons and electrons do not match; cations (positive) result from electron loss, and anions (negative) from electron gain.
Electron transfer occurs when sodium donates an electron to chlorine, forming ionic bonds (e.g., NaCl) due to opposite charges attracting.

Types of Bonds

Ionic bonds form between positively and negatively charged ions due to electron transfer.
Covalent bonds involve sharing electrons between atoms, forming the strongest and most common type of bond in biological molecules.
Water molecules (H₂O) are formed by covalent bonds, where electrons are shared to fill outer shells.

Energy and Thermodynamics

Energy is defined as the ability to do work and exists in various forms, including electrical, light, and heat energy.
Thermodynamics studies energy and energy transfer; the first law states energy cannot be created or destroyed, only transformed.
Energy transformations occur continuously, such as plants converting sunlight into chemical energy.
Living systems face challenges in obtaining usable energy, primarily deriving it from chemical energy in nutrients transformed into ATP for cellular work.
The second law of thermodynamics states that energy transfers are never entirely efficient; some energy is always lost as heat, increasing entropy (disorder).

Potential and Kinetic Energy

Kinetic energy is associated with motion; objects in motion can perform work.
Potential energy is stored energy based on an object's position, such as a lifted wrecking ball or compressed spring.
Potential energy can be transformed into kinetic energy when the stored energy is released, evident in swinging actions or falling objects.
Chemical energy is a form of potential energy within molecular bonds, released when bonds are broken, providing energy to living cells from food.

Description

This quiz covers the concepts of isotopes, their properties, and the significance of half-life in radioactive decay. It also explores electron configurations and their impact on chemical bonding among elements. Test your understanding of these fundamental topics in chemistry.