Chapter 2: Elements, Atomic Structure, Bonds, Chemical Reactions, and Water

Comprehensive vocabulary flashcards covering key definitions for elements, subatomic structure, chemical bonding, reactions, and water chemistry from Chapter 2.

Matter

Anything that takes up space and has mass, existing in four fundamental states of matter.

Element

A pure substance that cannot be broken down into other substances by chemical reactions, composed of only one type of atom.

Compound

A substance composed of two or more elements combined in a fixed ratio via a chemical reaction, which changes the physical properties of the individual elements.

Mixture

A combination of elements or substances that can be separated without chemical reactions, forming no new bonds and retaining individual properties without a fixed ratio.

Atom

The smallest unit of matter that retains the properties of an element, consisting of a central nucleus surrounded by electron shells.

Proton

A positively charged subatomic particle located in the atomic nucleus with a mass similar to that of a neutron.

Neutron

A neutral subatomic particle located in the atomic nucleus with a mass similar to that of a proton.

Electron

A negatively charged subatomic particle that orbits around the nucleus and has a mass roughly $1/2000$ of a proton or neutron.

Atomic Number ($Z$)

The number of protons present in the nucleus of an atom of a specific element, which does not change.

Atomic Mass ($A$)

The total number of protons and neutrons within an atom's nucleus, which can vary among different isotopes of an element.

Isotope

A form of an element with the same number of protons but a different number of neutrons, altering the atomic mass while behaving identically in chemical reactions.

Ion

An atom or molecule that has gained or lost one or more electrons, resulting in a net electrical charge.

Valence Shell

The electron shell located furthest from the nucleus of an atom.

Valence Electrons

Electrons located in the outermost shell (valence shell) of an atom that determine its chemical reactivity and behavior.

Covalent Bond

A chemical bond formed when valence electrons are shared between two atoms, typically nonmetals.

Single Covalent Bond

A covalent bond formed by the sharing of one pair of valence electrons between two atoms.

Double Covalent Bond

A covalent bond formed by the sharing of two pairs of valence electrons between two atoms.

Triple Covalent Bond

A covalent bond formed by the sharing of three pairs of valence electrons between two atoms.

Ionic Bond

A chemical bond formed by the electrostatic attraction between oppositely charged ions resulting from the complete transfer of electrons.

Cation

A positively charged ion formed when an atom loses one or more electrons, resulting in more protons than electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons, resulting in more electrons than protons.

Hydrogen Bond

A weak electrostatic attraction between a hydrogen atom and a highly electronegative atom such as nitrogen ($\text{N}$), oxygen ($\text{O}$), or fluorine ($\text{F}$).

Chemical Reaction

A process in which one or more starting substances change into one or more new substances with different properties.

Reactants

The starting materials that undergo chemical transformation during a chemical reaction.

Products

The final substances produced as a result of a chemical reaction.

Chemical Equilibrium

A state in a reversible reaction where the rate of the forward reaction equals the rate of the reverse reaction, maintaining constant concentrations.

Cohesion

The binding together of like molecules, such as water molecules held together by hydrogen bonds.

Adhesion

The clinging of one substance to another, such as water adhering to plant tissues or glass surfaces.

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid, elevated in water due to hydrogen bonding.

Solute

The substance that is dissolved in a solvent to form a solution.

Solvent

The dissolving agent of a solution that dissolves the solute.

Solution

A liquid that is a completely homogeneous mixture of two or more substances (solute dissolved in solvent).

Aqueous Solution

A solution in which water is the dissolving agent (solvent).

Acid

A substance with a pH less than $7$ that tastes sour, turns litmus paper red, feels corrosive, and increases hydrogen ion concentration ($[H^+]$).

Base

A substance with a pH greater than $7$ that tastes bitter or soapy, turns litmus paper blue, feels slippery, and reduces hydrogen ion concentration.

Neutralization Reaction

A chemical reaction between a strong acid and a strong base that produces salt and water, such as $\text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O}$.

pH Scale

A scale ranging from $0$ to $14$ that measures the relative concentration of hydrogen ions compared to distilled water.