chem 11 terms kys

Atom

The basic unit of a chemical element, consisting of a nucleus surrounded by electrons.

Atomic Mass

The mass of an atom, typically expressed in atomic mass units (amu).

Atomic Number

The number of protons in the nucleus of an atom, which determines the element's identity.

Atomic Radius

The distance from the nucleus to the outermost electron shell of an atom.

Avogadro’s Number

The number of atoms, molecules, or particles in one mole, approximately 6.022 × 10^23.

Bonding Pair

A pair of electrons shared between two atoms in a covalent bond.

Closed Shell

An electron shell that is completely filled with electrons.

Compound

A substance made of two or more elements chemically bonded together.

Electron

A subatomic particle with a negative charge, found in the electron cloud.

Electronegativity

A measure of the tendency of an atom to attract a bonding pair of electrons.

Element

A pure substance consisting of only one type of atom.

Energy Shells

The orbits or levels where electrons are found around the nucleus.

Group

A vertical column in the periodic table.

Ionic Bond

A chemical bond formed between two ions with opposite charges.

Ionization Energy

The energy required to remove an electron from an atom or ion.

Isotope

Atoms of the same element with different numbers of neutrons.

Lewis Dot Structure

A diagram showing the bonding between atoms of a molecule and lone pairs of electrons.

Lone Pair

A pair of valence electrons not shared with another atom.

Mass Number

The total number of protons and neutrons in an atom's nucleus.

Mechanical Mixture

A physical combination of substances that remain the same individual substances.

Mixture

A combination of two or more substances that are not chemically bonded.

Mole

A unit that measures the amount of a substance, based on the number of atoms or molecules.

Molecule

A group of atoms bonded together, representing the smallest unit of a chemical compound.

Neutron

A subatomic particle with no charge, found in the nucleus.

Nonpolar Covalent Bond

A type of chemical bond where two atoms share a pair of electrons equally.

Octet Rule

The principle that atoms tend to bond in such a way that they have eight electrons in their valence shell.

Open Shell

An electron shell that is not completely filled with electrons.

Period

A horizontal row in the periodic table.

Polar Covalent Bond

A type of chemical bond where a pair of electrons is unequally shared between two atoms.

Polyatomic Ion

An ion composed of two or more atoms covalently bonded.

Proton

A subatomic particle with a positive charge, found in the nucleus.

Pure substance

A substance that consists of only one type of particle.

Quantum Mechanics

A fundamental theory in physics that describes the physical properties of nature at the scale of atoms and subatomic particles.

Shared Electrons

Electrons that are shared between atoms in a covalent bond.

Single, Double, Triple bonds

Types of covalent bonds involving one, two, or three shared pairs of electrons between atoms.

Solution

A homogeneous mixture of two or more substances.

Valence Electrons

Electrons in the outermost shell of an atom that are involved in chemical bonding.

VSEPR Theory

A theory that predicts the shape of molecules based on the repulsion between electron pairs.

Accuracy

The closeness of a measured value to its true value.

Avogadro’s Number

The number of atoms, molecules, or particles in one mole, approximately 6.022 × 10^23.

Conversion factors

Ratios used to convert from one unit to another.

Directly Proportional

A relationship where one variable increases as the other increases.

Ideal Gas Law

An equation of state of an ideal gas: PV=nRT.

Indirectly Proportional

A relationship where one variable increases as the other decreases.

Molar Mass

The mass of one mole of a substance.

Mole

A unit that measures the amount of a substance, based on the number of atoms or molecules.

Precision

The closeness of two or more measurements to each other.

SATP

Standard Ambient Temperature and Pressure 24.79L

Scientific Constant

A fixed value that describes a physical property.

Scientific Notation

A way of expressing numbers that are too large or too small to be conveniently written in decimal form.

Significant Figures

Digits in a number that carry meaningful contributions to its measurement accuracy.

STP

Standard Temperature and Pressure 22.7L

Uncertainty

An estimate of how much a measured or calculated value deviates from the true value.

Unit conversions

Ratios used to convert from one unit to another.

Acid-Base Neutralization

A reaction between an acid and a base to produce a salt and water.

Chemical Reaction

A process in which substances react to form new substances.

Coefficients

Numbers used to balance chemical equations.

Combustion Reaction

A reaction where a substance reacts with oxygen, releasing energy as heat and light.

Decomposition Reaction

A reaction where a single compound breaks down into two or more simpler substances.

Double Replacement Reaction

A reaction where parts of two compounds exchange places to form two new compounds.

Endothermic Reaction

A reaction that absorbs energy from its surroundings.

Enthalpy

The heat content of a system at constant pressure.

Excess Reagent

A reactant that remains after a chemical reaction is complete.

Exothermic Reaction

A reaction that releases energy to its surroundings.

Limiting Reagent

The reactant that is entirely consumed when the reaction goes to completion.

Percent Purity

The ratio of the mass of pure product obtained to the theoretical mass.

Percent Yield

The ratio of the actual yield to the theoretical yield expressed as a percentage.

Products

Substances formed as the result of a chemical reaction.

Reactants

Substances that undergo a chemical reaction.

Single Replacement Reaction

A reaction where an element reacts with a compound, displacing an element from it.

Stoichiometry

The calculation of reactants and products in chemical reactions.

Subscripts

Numbers written below the line that tell how many atoms of a given type are in a compound.

Synthesis Reaction

A reaction where two or more simple substances combine to form a more complex substance.

Ionic solid

A solid composed of ions bonded together in a lattice structure.

Ionization

The process by which an atom or molecule acquires a negative or positive charge by gaining or losing electrons.

“Like dissolves like”

A principle stating that polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar solutes.

Aqueous Solution

A solution in which the solvent is water.

Boiling

The transition of a liquid to a gas.

Boiling Point

The temperature at which a liquid changes to a gas.

Concentration

The amount of solute dissolved in a given volume of solvent.

Condensing

The transition of a gas to a liquid.

Crystal lattice

A structure in which ions are arranged in a repeating pattern.

Dilution

The process of reducing the concentration of a solute in solution, usually by mixing with more solvent.

Dipole moment

A measure of the separation of positive and negative charges in a molecule.

Dipole-Dipole forces

Forces of attraction between polar molecules.

Dissociation and Ionization

The separation of ions in a solution by the action of a solvent.

Entropy

A measure of the disorder or randomness in a system.

Freezing

The transition of a liquid to a solid.

Gas

A state of matter with no fixed shape and no fixed volume.

Homogenous Mixture

A mixture that has uniform composition and properties throughout.

Hydrogen Bonds

A type of weak chemical bond formed between an electronegative atom and a hydrogen atom bound to another electronegative atom.

Intermolecular forces

Forces of attraction between molecules.

Ionic Bond

A chemical bond formed between two ions with opposite charges.

Lewis-Dot Structures

A diagram showing the bonding between atoms of a molecule and lone pairs of electrons.

Liquid

A state of matter with a definite volume but no definite shape.

London forces

Weak intermolecular forces resulting from instantaneous dipoles in molecules.

Melting

The transition of a solid to a liquid.

Melting Point

The temperature at which a solid changes to a liquid.

Molarity

A measure of the concentration of solute in a solution in terms of amount of substance in a given volume.

Molecular solid

A solid composed of molecules held together by intermolecular forces.