Capítulo 2: Atoms and Elements - Vocabulary Flashcards

Vocabulary-style flashcards covering key terms and definitions from the lecture notes.”

Atom

The basic unit of a chemical element; in the notes it is described as a small indivisible particle that makes up matter.

John Dalton

Proposed the first scientific atomic theory (1803), describing atoms as tiny indivisible particles.

Dalton’s Postulates

Key ideas: matter is made of atoms; atoms are indivisible; atoms of the same element are identical; atoms of different elements have different properties; compounds form from simple whole-number ratios; chemical changes rearrange atoms.

Conservation of Mass

In a chemical reaction, the total mass of the reactants equals the total mass of the products.

Cathode Ray

A beam of electrons produced by applying electricity; travels from the cathode (negative) to the anode (positive) in a tube.

Electron

Subatomic particle with a negative charge; discovered by Thomson; has a charge-to-mass ratio of -1.76 x 10^8 C/g.

J. J. Thomson

Scientist who demonstrated that cathode rays are negatively charged particles, leading to the discovery of the electron.

Millikan Oil-Drop Experiment

Experiment that determined the elementary charge of the electron (-1.6022 x 10^-19 C) and its mass (~9.10 x 10^-28 g).

Nucleus

A small, dense region at the center of the atom containing most of its mass and positive charge (Rutherford's nuclear model).

Proton

Positively charged subatomic particle located in the nucleus; discovered by Rutherford.

Neutron

Electrically neutral subatomic particle in the nucleus; discovered by James Chadwick (1932).

Isotope

Atoms of the same element that have different numbers of neutrons and thus different masses.

Atomic number (Z)

The number of protons in an atom; identifies the element.

Mass number (A)

The total number of protons and neutrons in an atom (per isotope).

Atomic mass unit (amu)

Unit used to express atomic and molecular masses.

Isotopic abundance

Fraction or percentage of a given isotope found in a natural sample.

Average atomic mass

Weighted average mass of an element’s isotopes based on their abundances; expressed in amu.

Periodic Table

Organization of elements by increasing atomic number; rows are periods and columns are groups; elements in a group share similar properties.

Alkali metals (Group 1A)

Reactive metals such as Li, Na, K, Rb, Cs, Fr.

Alkaline earth metals (Group 2A)

Reactive metals such as Be, Mg, Ca, Sr, Ba, Ra.

Chalcogens (Group 6A)

Nonmetals including O, S, Se, Te, Po.

Halogens (Group 7A)

Highly reactive nonmetals such as F, Cl, Br, I, At.

Noble gases (Group 8A)

Inert or rare gases such as He, Ne, Ar, Kr, Xe, Rn.

Metals

Elements on the left that tend to lose electrons to form cations and are good conductors of electricity.

Nonmetals

Elements on the right (except H) that tend to gain electrons to form anions; typically poor conductors.

Metalloids

Elements with properties between metals and nonmetals; located along the boundary line (excluding Al, Po, At in some depictions).

Ionic bond

Bond formed by the transfer of electrons between a metal and a nonmetal; compounds consist of cations and anions.

Chemical formula

Notation that shows the number of atoms of each element in a substance; subscripts indicate atom counts.

Diatomic molecules

Seven elements that exist naturally as diatomic molecules: H2, N2, O2, F2, Cl2, Br2, I2.

Empirical formula

The simplest whole-number ratio of atoms in a compound.

Molecular formula

The actual number of atoms of each element in a molecule.

Structural formula

Shows how atoms are connected and arranged in a molecule.

Ion

Atom or molecule with a net electric charge due to gain or loss of electrons.

Cation

Positively charged ion; typically forms from metals by loss of electrons.

Anion

Negatively charged ion; typically forms from nonmetals by gain of electrons.

Common cations

Examples include H+, Na+, K+, NH4+, Mg2+, Ca2+ (ions essential in chemistry and biology).

Common anions

Examples include Cl-, NO3-, SO4^2-, OH-, CO3^2- (frequently encountered in inorganic chemistry).

Oxianions naming (-ite, -ate)

Oxoanions: the -ite form has fewer oxygens than the -ate form; hypo- and per- indicate the least and most oxygens respectively (e.g., chlorite vs chlorate; hypochlorite vs perchlorate).

Acid nomenclature

Acids are named from their anions: -ide becomes - hydro- + -ic; -ite becomes -ous; -ate becomes -ic; acids with -ide often use hydro- naming (e.g., HCl → hydrochloric acid).

Binary molecular nomenclature

Name the element farther to the right first; if same group, name the one higher in the table; add -ide to the second element and use prefixes to indicate numbers (e.g., Cl2O → dichlorine monoxide; NF3 → nitrogen trifluoride).

Hydrates

Compounds with water of hydration; prefixes mono-, di-, etc., used with -hydrate.

Nomenclature of inorganic compounds

Name the cation first; if the anion is an element, end with -ide; if polyatomic, use its name; metals with multiple charges use Roman numerals in parentheses.

Organic chemistry

Branch of chemistry studying carbon-containing compounds; has its own nomenclature system.

Alkanes (alkanes)

Saturated hydrocarbons with general formula CnH2n+2; first syllable indicates the number of carbons (meth-, eth-, prop-, but-, etc.).

Alkenes (olefins)

Hydrocarbons with one or more double bonds; general formula CnH2n.

Alkynes

Hydrocarbons with triple bonds; general formula CnH2n-2.

Alcohols

Organic compounds containing -OH; suffix -ol. Example: ethanol.

Amines

Functional group R-NH2; example methylamine.

Carboxylic acids

Functional group -COOH; acidic; example acetic acid (CH3CO2H).

Aldehydes

Functional group -CHO; carbonyl carbon at the end of the chain.

Esters

Functional group -COO-R where R is an alkyl group.

Amide

Functional group -CONH2.

Ether

Functional group R-O-R; example dimethyl ether.

Ketone

Functional group -C(O)-; carbonyl group between two carbon atoms.

Mass spectrometry

Analytical technique for measuring atomic and molecular masses with high precision.