General Chemistry (CHEM 111) - Chapter 2 Elements and Compounds

Flashcards covering key vocabulary, definitions, and concepts from General Chemistry Chapter 2, 'Elements and Compounds'.

Atom (ancient concept)

Meaning 'unable to be divided', first proposed by ancient Greek philosopher Demokritos (~ B.C. 500).

Atomism

The first scientific theory of the atom, described in 1808 by John Dalton.

Atom (modern definition)

The smallest unit of an element that retains its chemical properties, and the smallest unit in a chemical reaction.

Atomic mass unit (amu)

A unit of mass, where 1 \text{ amu} = 1.67 \times 10^{-27} \text{ kg}, equal to 1/12 the mass of a carbon atom.

Dalton (unit)

A unit of mass equivalent to 1 \text{ amu}.

Electron cloud

The region formed by fast-moving electrons around the nucleus, appearing like a big cloud.

Atomic number (Z)

The number of protons in an atom, which also equals the number of electrons in a charge-neutral state.

Atomic Number (Z) Formula

Z = \text{number of protons} (also equal to the number of electrons in a neutral atom).

Mass number (A)

The total number of protons and neutrons in an atom.

Mass Number (A) Formula

A = \text{number of protons} + \text{number of neutrons}.

Ion

An atom with an unequal number of protons and electrons.

Cation

An ion with an overall positive charge, having more protons than electrons.

Anion

An ion with an overall negative charge, having more electrons than protons.

Isotopes

Atoms of the same element (same atomic number and number of protons) but with different masses due to a different number of neutrons.

Atomic weight

The weighted average of the atomic masses of all naturally occurring isotopes of an element.

Alkali metals

Elements in Group I of the periodic table; shiny, malleable, excellent conductors, react violently with water, and lose electrons to form cations.

Halogens

Elements in Group VII of the periodic table; nonmetals, do not conduct electricity, highly reactive, form strong acids with water, and gain electrons to form anions.

Noble gases

Elements in Group VIII of the periodic table (e.g., helium, neon, argon); characterized by their difficulty to react with other elements.

Alkaline earth metals

Elements in Group 2 (2A) of the periodic table.

Chalcogens

Elements in Group 16 (6A) of the periodic table.

Transition elements

Elements located in Groups 4-12 (3B-8B, 1B and 2B) of the periodic table.

Lanthanides

A series of elements that are part of period 6 (atomic numbers 57–71).

Actinides

A series of elements that are part of period 7 (atomic numbers 89–103).

Metals

Elements that are typically solids at room temperature (except Hg), shiny, conduct electricity, are ductile and malleable, form alloys, and tend to give up electrons in chemical reactions.

Nonmetals

Elements (except hydrogen) found on the right side of the Periodic Table; generally do not conduct electricity (except graphite) and tend to accept electrons in chemical reactions.

Metalloids

Elements that exhibit some properties of metals and some of nonmetals, such as boron, silicon, germanium, arsenic, antimony, and tellurium.

Valence electrons

Electrons found in the outermost layer or shell of an element.

Core electrons

Any electrons in an atom that are not valence electrons, located deeper within the atom.

Compounds

A combination of at least two or more atoms of different elements bonded together in a defined ratio.

Ionic bond

A strong attractive force between cations and anions, generally formed between metals and nonmetals.

Octet rule

The principle that atoms tend to react chemically to achieve eight valence electrons in their outer shell, mimicking noble gas electron configurations.

Monoatomic ion

An ion formed from a single atom that has gained or lost electrons.

Cation naming convention

For non-transition metals, the element name followed by 'ion' (e.g., potassium ion); for transition metals, the element name followed by (charge in Roman numbers) and 'ion' (e.g., chromium(II) ion).

Anion naming convention

The first part of the element name followed by the suffix '-ide' and then 'ion' (e.g., bromide ion, oxide ion).

Polyatomic Ions

A group of atoms that are covalently bonded together but collectively carry a net electrical charge.

Covalent bonds

Bonds formed when two or more non-metal atoms share their electrons.

Molecular covalent compounds

Compounds where discrete molecules are held together by covalent bonds (e.g., H2O).

Network covalent compounds

Compounds where atoms are held together by an extended network of covalent bonds throughout the entire structure (e.g., Silicon Dioxide).

Covalent compound naming rules

The first element is named first, followed by the second with an '-ide' ending; prefixes are used to indicate the number of each type of atom, but 'mono' is not used for the first element.

Allotropes

Different forms of the same element that differ in their physical and chemical properties (e.g., diamond, graphite, fullerene for carbon).