Chapter 2: Atomic Theory, Ions, Isotopes, and the Periodic Table

A set of practice flashcards covering Dalton's atomic theory, ions, isotopes, atomic mass, periodic table organization, types of bonds, and polyatomic ions.

What are the five postulates of Dalton's Atomic Theory?

1) Law of Conservation of Matter: atoms are neither created nor destroyed in a chemical change; 2) Elements are composed of atoms; 3) Atoms of the same element are identical in properties; 4) Atoms of different elements have different properties; 5) Compounds form when atoms of different elements combine in simple whole-number ratios; in reactions atoms are rearranged, not destroyed.

The smallest unit of matter that can participate in a chemical change is an .

atom

Define an ion.

An atom or group of atoms with a net electric charge due to loss or gain of electrons.

An atom that loses electrons becomes a __.

cation

An atom that gains electrons becomes an __.

anion

What is an Atomic Mass Unit (amu)?

A practical unit for describing atomic and subatomic masses; 1 amu is 1/12 the mass of a carbon-12 atom.

What is the Mass Number (A) of an atom?

A = number of protons + number of neutrons.

What is the elementary charge of a single electron in Coulombs?

1.602 x 10^-19 C (the charge unit, with electrons having a negative charge).

What is an isotope?

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

How do you calculate the average atomic mass from isotopes?

Weighted average: Overall mass = sum (fractional abundance × isotopic mass) for all naturally occurring isotopes.

How is an isotope typically represented symbolically?

A^Z X, where A is the mass number (superscript) and Z is the atomic number (subscript) for element X.

What are the main group (representative) elements in IUPAC notation?

Groups 1, 2, and 13–18; they are the main group elements (not including the transition metals).

Who independently contributed to the development of the periodic table and predicted undiscovered elements?

Dmitri Mendeleev and Lothar Meyer.

State the Periodic Law.

The properties of the elements are periodic functions of their atomic numbers.

How are elements classified by properties?

Metals: shiny, malleable, good conductors; Nonmetals: dull, poor conductors; Metalloids: intermediate properties.

What is the key difference between ionic and covalent bonds?

Ionic: transfer of electrons creating ions (metal + nonmetal). Covalent: sharing of electrons (usually nonmetals).

What is a diatomic molecule?

A molecule composed of two atoms (e.g., H2, N2, O2, F2, Cl2, Br2, I2).

What is the empirical formula of a compound?

The simplest whole-number ratio of atoms in a compound; may differ from its molecular formula.

What is a polyatomic ion?

A charged species made up of two or more atoms (e.g., sulfate SO4^2−, ammonium NH4^+).

Name the common polyatomic ion: sulfate.

SO4^2−

Name the common polyatomic ion: ammonium.

NH4^+

Name the common polyatomic ion: hydroxide.

OH−

Which block on the periodic table contains the transition metals?

The d-block (groups 3–12 in many representations; transition metals).

What group do alkali metals belong to and what is a typical ion charge for them?

Group 1 (1A); they form +1 cations (e.g., Na^+).

What is the defining characteristic of metalloids?

Elements with intermediate properties between metals and nonmetals; can conduct electricity/moderately.

What are the two rows of inner transition metals called?

Lanthanides (top) and Actinides (bottom).

What is the difference between a monatomic ion and a polyatomic ion?

Monatomic ions come from a single atom; polyatomic ions come from a molecule that has gained or lost electrons.

Give an example of a diatomic molecule and its type of bonding.

O2 is a covalently bonded diatomic molecule (two oxygen atoms sharing electrons).