Ch.1-3 CHEM1211K

Anion

A negatively charged ion formed when an atom gains electrons (e.g., Cl⁻).

Cation

A positively charged ion formed when an atom loses electrons (e.g., Na⁺).

Electron

A negatively charged (-1) subatomic particle with negligible mass located outside the nucleus.

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons (different mass numbers).

Mass

The measure of the amount of matter in an object, typically measured in grams (g) or atomic mass units (amu).

Neutron

A neutral (0 charge) subatomic particle with a mass of ~1 amu located inside the nucleus.

Proton

A positively charged (+1) subatomic particle with a mass of ~1 amu located inside the nucleus; defines element identity.

Sublimation

The phase transition in which a substance changes directly from a solid to a gas without becoming a liquid.

Covalent Bond

A chemical bond formed when two nonmetal atoms share one or more pairs of electrons.

Ionic Bond

A chemical bond formed by electron transfer from a metal to a nonmetal, creating oppositely charged ions that attract.

Metallic Bond

A chemical bond formed by electrostatic attraction between metal cations and a delocalized "sea of electrons."

Alkali Metals

Group 1A (except Hydrogen): Extremely reactive metals with 1 valence electron; form +1 cations (e.g., Na, K).

Alkaline Earth Metals

Group 2A: Reactive metals with 2 valence electrons; form +2 cations (e.g., Mg, Ca).

Halogens

Group 7A / Group 17: Highly reactive nonmetals with 7 valence electrons; form -1 anions (e.g., F, Cl, Br).

Noble Gases

Group 8A / Group 18: Extremely stable, unreactive nonmetals with full valence electron shells (8 valence electrons; He has 2).

Metals

Elements on the left and middle of the periodic table; shiny, malleable, ductile, and good conductors of heat/electricity.

Metalloids

Elements along the staircase line (B, Si, Ge, As, Sb, Te); exhibit intermediate properties between metals and nonmetals.

Nonmetals

Elements on the upper right side (plus Hydrogen); dull, brittle, and poor conductors (insulators).

Pure Substance

Matter with a constant, uniform composition and distinct properties; consists of elements or compounds only.

Mixture

A physical combination of two or more substances that retain their individual identities and can be physically separated.

Pure Element

A pure substance composed of only one type of atom (e.g., C, O₂); cannot be chemically broken down into simpler substances.

Pure Compound

A pure substance composed of two or more different elements chemically bonded in fixed ratios (e.g., H₂O, NaCl).

Homogeneous Mixture

A mixture with a uniform composition throughout; individual components are not visible (e.g., salt water, air).

Heterogeneous Mixture

A mixture with a non-uniform composition; individual phases or components remain distinct and visible (e.g., salad, oil & water).

Atomic Element

An element that exists naturally in nature as single, unbonded individual atoms (e.g., Ne, Ar, Fe).

Molecular Element

An element that naturally exists as two or more identical atoms bonded together (e.g., diatomics like H₂, O₂, N₂, Cl₂).

Ionic Compound

A neutral compound made of metal cations and nonmetal anions bound by ionic bonds (e.g., NaCl, MgO).

Molecular / Covalent Compound

A compound formed strictly between nonmetal atoms sharing electrons via covalent bonds (e.g., CO₂, H₂O).

Atomic Number (Z)

The number of protons in an atom's nucleus. Located as an integer on the periodic table; defines the element's identity.

Atomic Mass / Mass Number

Atomic Mass is the weighted average mass of naturally occurring isotopes (decimal on periodic table). Mass Number (A) = Protons + Neutrons.

Isotopic Notation Symbol

Superscript (A) = Mass Number (Protons + Neutrons) on top-left. Subscript (Z) = Atomic Number (Protons) on bottom-left. Charge on top-right.

How to Find Protons

Protons = Atomic Number (Z). Found directly on the periodic table for each element.

How to Find Neutrons

Neutrons = Mass Number (A) - Atomic Number (Z). Subtract atomic number (protons) from rounded mass number.

How to Find Electrons

In a neutral atom: Electrons = Protons. In Cation (+): Electrons = Protons - Charge. In Anion (-): Electrons = Protons + |Charge|.

Atom

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

Molecule

A group of two or more atoms chemically bonded together to form the smallest fundamental unit of a chemical compound.

Element

Made up of atoms; (ex: Au (gold) )

Compound

made up of molecules; an assembly of 2 or more atoms ( ex: H2O )

Ion

positively or negatively charged particles

intensive property

doesn’t depend on amount (ex: melting point, flammable, temperature)

extensive property

depends on amount (ex: mass, volume, length(