General Chemistry I - Chapter 2: Atoms, Molecules and Ions

A comprehensive set of practice flashcards covering Dalton’s atomic theory, atomic structure, isotopes, ions, chemical formulas, periodic table organization, bonding, and nomenclature from the notes.

According to Dalton's atomic theory, what are atoms?

The smallest unit of an element that can participate in a chemical change; matter is composed of exceedingly small particles called atoms.

What does the law of conservation of matter state?

During a chemical change, mass is conserved; the total mass present before and after the change remains constant.

What does the law of definite proportions state?

All samples of a pure compound contain the same elements in the same proportion by mass.

What does the law of multiple proportions state?

When two elements react to form more than one compound, a fixed mass of one element combines with masses of the other element in small, whole-number ratios.

Define an isotope.

Atoms of the same element that have different masses due to a different number of neutrons.

What is the atomic number Z?

Number of protons in the nucleus; equals the number of electrons in a neutral atom.

What is the mass number A?

Total number of protons and neutrons in the nucleus (A = Z + number of neutrons).

What is an ion?

An atom or group of atoms with a net positive or negative charge.

What is a cation?

An ion with a positive charge, formed when atoms lose electrons.

What is an anion?

An ion with a negative charge, formed when atoms gain electrons.

What is 1 amu equal to?

1.6605 × 10^-24 g; defined as 1/12 the mass of a carbon-12 atom.

What is the fundamental unit of charge, e?

e = 1.602 × 10^-19 C.

What is the purpose of an atomic mass unit (amu)?

To express atomic and molecular masses; 1 amu is 1/12 the mass of carbon-12; carbon-12 is defined as 12 amu.

What is a chemical symbol, and what is the capitalization rule?

A one- or two-letter abbreviation for an element; only the first letter is capitalized.

In isotope notation, what do A, Z, and X represent?

A = mass number; Z = atomic number; X = element symbol (e.g., 1H, 2H, 3H denotes isotopes of hydrogen).

What is the difference between a molecular formula, an empirical formula, and a structural formula?

Molecular formula shows exact atom counts; empirical formula shows the simplest whole-number ratio; structural formula shows how atoms are bonded.

What is an allotrope?

One of two or more distinct forms of an element (e.g., O2 vs O3; S8 for sulfur).

What is a diatomic molecule?

A molecule consisting of two atoms (e.g., H2, N2, O2, F2, Cl2, Br2, I2; HCl is also diatomic).

What is a polyatomic molecule?

A molecule containing more than two atoms (e.g., H2O, NH3, CH4, O3).

What is a monatomic vs polyatomic ion?

Monatomic ions contain a single atom; polyatomic ions contain more than one atom.

What are the two main types of chemical bonds?

Ionic bonds (electrons transferred) and covalent bonds (electrons shared).

What is an ionic compound?

A compound held together by ionic bonds between cations and anions; typically solids with high melting points; non-conductive as a solid but conductive when molten or dissolved.

How do you determine the formula of an ionic compound from its ions?

Balance the charges so the total positive and negative charges cancel; polyatomic ions may be used; parentheses indicate groups of atoms acting as a unit.

What is the rule for naming ionic compounds containing transition metals?

Use the Stock system with a Roman numeral to indicate the metal's charge (e.g., FeCl3 = iron(III) chloride).

How are binary molecular (covalent) compounds named?

Name the more metallic element first, then the less metallic element with -ide; use Greek prefixes to indicate the number of atoms; mono- is usually omitted for the first element.

How are acids named in binary acids?

Hydrogen is replaced with hydro-, the second element name is turned to -ic, and the word acid is added (e.g., HF -> hydrofluoric acid).

How are oxyacids named?

Omit hydrogen; name the anion root, replace -ate with -ic or -ite with -ous, then add acid.

What is the naming rule for oxyanions?

-ate suffix for the ion with more oxygens; -ite for fewer; prefixes (per-, hypo-) used for more complex series.

What is a hydrate and give an example?

A compound with a specific number of water molecules attached; e.g., CuSO4·5H2O is copper(II) sulfate pentahydrate.

What is an oxide? (as used in hydrate naming problems)

A compound containing oxide O^2- or related oxide in formulas like Na2O, CaO, etc.

What is the periodic law as described in the notes?

The properties of elements are periodic functions of their atomic numbers; elements in the same group have similar properties.

How is the periodic table organized?

Increasing atomic number with groups (vertical columns) and periods (horizontal rows).

Name the key groups shown in the notes: 1, 2, 17, 18.

Group 1: Alkali metals; Group 2: Alkaline earth metals; Group 17: Halogens; Group 18: Noble gases.

What classifications describe main group elements, transition metals, and inner transition metals?

Main group elements (groups 1,2,13-18); Transition metals (groups 3-12); Inner transition metals (lanthanides and actinides).

What is the difference between metals and nonmetals in terms of appearance and conductivity?

Metals are shiny, malleable, good conductors; nonmetals are dull and poor conductors; metalloids have properties in between.

What is the typical ionic charge pattern for main-group elements when forming ions?

Group 1 metals form +1 ions; Group 2 metals form +2 ions; Group 17 nonmetals form -1 ions; Group 16 nonmetals form -2 ions (with variations for transition metals).

What is the significance of monatomic vs polyatomic ions in formulas?

Ions are represented as discrete units; polyatomic ions are treated as a single unit with a fixed charge in formulas.

Which elements exist naturally as monatomic gases?

The noble gases (Group 18: He, Ne, Ar, Kr, Xe, Rn).