Life's Chemistry, Chemical Bonds, and Thermodynamics

Flashcards reviewing atomic structure, atomic mass, chemical bonds, electronegativity, energy types, thermodynamics, and chemical reactions.

What is an element?

A fundamental substance that consists of only one kind of atom.

Which four elements are the most abundant in the living system?

Hydrogen, carbon, oxygen, and nitrogen.

How is an element defined?

An element is defined by the number of protons in an atom.

What are the three major components of an atom and their charges?

Protons (positively charged particles), neutrons (uncharged particles), and electrons (negatively charged particles).

Where are the components of an atom located?

Protons and neutrons are clustered in the nucleus, while rapidly moving electrons are outside the nucleus in electron shells.

In what unit is atomic mass measured?

Daltons ($Da$).

What is the difference between atomic number and mass number?

Atomic number is the number of protons in a nucleus, while mass number is the sum of protons and neutrons.

What is an atomic orbital?

A defined area within an electron shell in which electrons move.

What is the Octet rule and what element is the exception to it?

The rule stating an atom will lose, gain, or share electrons to achieve a stable configuration of $8$ electrons in its most outer shell; hydrogen is the exception.

What is electronegativity and what factors determine it?

Electronegativity is an atom's tendency to attract electrons from another atom. It depends on the number of electrons in the outermost shell (more electrons means higher electronegativity) and how close electrons are to the nucleus (closer electrons mean greater electronegativity).

How stable are elements with atomic numbers $95$ through $118$?

Elements with atomic numbers $95$ to $118$ are highly unstable.

What is the difference between a molecule and a compound?

A molecule is formed when two or more atoms join together chemically, whereas a compound is a molecule formed by at least two different elements.

How do covalent bonds form?

Covalent bonds form when two atoms share one or more pairs of electrons to attain a stable electron configuration.

What two covalent bond characteristics influence the properties of molecules?

Orientation (length, angle, and direction of bonds between any two elements are always the same) and Strength/Stability (covalent bonds are very strong).

What is the difference between nonpolar and polar covalent bonds?

In nonpolar bonds, electrons are shared equally (such as between carbon and hydrogen). In polar bonds, electrons are pulled closer to the nucleus of the more electronegative atom.

What is an ionic bond and what are the two types of ions?

An ionic bond occurs when a highly electronegative atom pulls one or more electrons away from an atom with low electronegativity. The resulting ions are cations ($+$) and anions ($-------$).

What is a dipole and what are dipole-dipole interactions?

A dipole is the separation of opposite electric charges (such as in a polar covalent bond). Dipole-dipole interactions are weak interactions where slightly charged atoms interact with other atoms.

What is a hydrogen bond?

An attraction between a slightly positively charged covalently bonded hydrogen and a slightly negatively charged covalently bonded nitrogen or oxygen.

What are Van der Waals interactions?

Attractions between oppositely charged atoms caused by the movement of electrons resulting in small temporary dipoles.

How is energy defined in the lecture notes?

Energy is the capacity to produce a change.

What forms of energy fall under kinetic energy and potential energy?

Kinetic energy (energy of movement) includes thermal, sound, and electromagnetic energy. Potential energy (stored energy) includes gravitational, elastic, chemical, and nuclear energy.

What are the First and Second Laws of Thermodynamics?

1st Law: Energy cannot be created or destroyed. 2nd Law: When an energy transformation occurs, there is an increase in entropy (a measure of disorder, how spread out energy is, or how much is unusable).

What is a chemical reaction and what equation describes hydrolysis?

A chemical reaction occurs when atoms combine or change their bonding partners. Hydrolysis is represented by: $\text{Complex molecule} + H_2O \rightarrow \text{simpler molecules}$.

What are the chemical formulas given for synthesis, decomposition, and exchange reactions?

Synthesis: $A + B \rightarrow AB$; Decomposition: $AB \rightarrow A + B$; Exchange: $AB + CD \rightarrow AC + BD$.