AP Chemistry Semester 1

Can one count particles directly while performing laboratory work?

No

There must be a connection between the ______ of substances reacting and the ______ of particles undergoing chemical changes

Masses, actual number

Why must there be a connection between the masses of substances reacting and the actual number of particles undergoing chemical changes?

One cannot count particles directly while performing laboratory work

What is Avogadro’s number?

6.02×10^(23)

Avogadro’s number provides the connection between:

The number of moles in a pure sample of a substance and the number of constituent particles (or formula units) of that substance

Expressing the mass of an individual atom or molecule in ______ is useful

Atomic mass units (amu)

Why is it useful to express the mass of an individual atom or molecule in atomic mass units (amu)?

The average mass in amu of one particle (atom or molecule) or formula unit of a substance will always be numerically equal to the molar mass of that substance in grams

There is a quantitative connection between the ______ of a substance and the number of particles that the substance contains

Mass

There is a quantitative connection between the mass of a substance and the ______ that the substance contains

Number of particles

The mass spectrum of a sample containing a single element can be used to determine the:

Identity of the isotopes of that element and the relative abundance of each isotope in nature

The average atomic mass of an element can be estimated from the:

Weighted average of the isotopic masses

How can the average atomic mass of an element be estimated from the weighted average of the isotopic masses?

By using the mass of each isotope and its relative abundance

Why do all atoms of a given element not have the same mass?

They have different amounts of neutrons

Pure substances are composed of:

Either individual molecules or atoms or ions held together in fixed proportions

Atoms and ions being held together in fixed proportions is described by a:

Formula unit

According to the law of definite proportions, the ratio of the masses of the constituent elements in any pure sample of that compound is:

Always the same

The chemical formula that lists the lowest whole number ratio of atoms of the elements in a compound is the:

Empirical formula

Pure substances contain atoms, molecules, or formula units of:

A single type

Mixtures contain atoms, molecules, or formula units of:

Two or more types

Can relative proportions of atoms, molecules, or formula units in mixtures vary?

Yes

Elemental analysis can be used to:

Determine the relative numbers of atoms in a substance and to determine its purity

The atom is composed of:

Negatively charged electrons and a positively charged nucleus

The positively charged nucleus is made of:

Protons and neutrons

Coulomb’s law is used to calculate the:

Force between two charged particles

Coulomb’s law:

F is proportional to (q1q2)/r²

In atoms and ions, the electrons can be thought of as being in:

Shells (energy levels) and subshells (sublevels)

Electrons being in shells and subshells is described by the:

Ground-state electron configuration

Inner electrons are called:

Core electrons

Outer electrons are called:

Valence electrons

The electron configuration is explain by:

Quantum mechanics

The quantum mechanics used to explain electron configuration is delineated in:

Aufbau principle

The quantum mechanics used to explain electron configuration is exemplified in:

Periodic table of elements

The relative energy required to remove an electron from different subshells of an atom or ion or from the same subshell in different atoms or ions can be estimated through a qualitative application of:

Coulomb’s law

The relative energy required to remove an electron from the same subshell in different ions is called:

Ionization energy

The energy required to remove an electron from different subshells of an atom or ion or from the same subshell in differemt atoms or ions is related to:

The distance from the nucleus and effective (shield) charge of the nucleus

The energies of the electrons in a given shell can be measured experimentally with:

Photoelectron spectroscopy

Short form of photoelectron spectroscopy:

PES

The position of each peak in the PES spectrum is related to:

The energy required to remove an electron from the corresponding subshell

The relative height of each peak on the PES spectrum is (ideally) proportional to:

The number of electrons in that subshell

The organization of the periodic table is based on patterns of:

Recurring properties of the elements

Patterns of recurring properties of elements are explain by:

Patterns of ground-state electron configurations and the presence of completely or partially filled shells (and subshells of electrons in atoms)

Trends in atomic properties within the periodic table are called:

Periodicity

Periodicity can be predicted by:

The position of the element on the periodic table

Periodicity can be qualitatively understood using:

Coulomb’s law, the shell model, and concepts of shielding and effective nuclear charge

Atomic properties include:

Ionization energy, atomic and ionic radii, electron affinity, electronegativity

Periodicity is useful to:

Predict/estimate values of properties in the absence of data

The likelihood that two elements will form a chemical bond is determined by:

Interactions between the valence electrons and nuclei of elements

Elements in the same column of the periodic table tend to form:

Analogous compounds

Typical charges of atoms in ionic compounds are governed by the:

Number of valence electrons

Typical charges of atoms in ionic compounds are predicted by:

Their location on the periodic table

Electronegativity values for the representative elements increase/decrease going from left to right across a period

Increase

Electronegativity values for the representative elements increase/decrease going down a group

Decrease

Trends in electronegativity values can be understood qualitatively through the:

Electronic structure of the atoms, the shell model, and Coulomb’s law

Valence electrons shared between atoms of similar electronegativity constitute a:

Nonpolar covalent bond

Bonds between carbon and hydrogen are effectively polar/nonpolar

Nonpolar

Carbon is slightly more/less electronegative than hydrogen

More

Valence electrons shared between atoms of unequal electronegativity constitute a:

Polar covalent bond

The atom with a higher electronegativity will develop a ______ relative to the other atom in the bond

Partial negative charge

In single bonds, greater differences in electronegativity lead to:

Greater bond dipoles

Do all polar bonds have ionic character?

Yes

The difference between ionic and covalent bondng is distinct / a continuum

A continuum

Is difference in electronegativity the only factor in determining if a bond should be designated as ionic or covalent?

No

Bonds between a metal and nonmetal are:

Ionic

Bonds between two nonmetals are:

Covalent

What is the best way to characterize the type of bonding?

Examination of the properties of a compound

In a metallic solid, the valence electrons from the metal atoms are considered to be:

Delocalized and not associated with any individual atom

What is a useful representation for describing the interactions between atoms?

A graph of potential energy vs distance between atoms

Graphs of potential energy vs distance between atoms illustrate:

Equilibrium bond length and bond energy

The separation between atoms at which the potential energy is lowest

Equilibrium bond length

The energy required to separate atoms

Bond energy

In a covalent bond, the bond length is influenced by:

Size of atom’s core and bond order

Examples of bond order:

Single, double, triple

Bonds with a higher order are longer/shorter

Shorter

Bonds with a higher order have larger/smaller bond energies

Larger

What can be used to understand the strength of interactions between cations and anions?

Coulomb’s law

Larger charges lead to stronger/weaker interactions

Stronger

Why do larger charges lead to stronger interactions?

Interaction strength is proportional to the charge on each ion

Smaller ions lead to stronger/weaker interactions

Stronger

Why do smaller ions lead to stronger interactions?

Interaction strength increases as the distance between the nuclei decreases

Nuclei means:

Centers of ions

The cations and anions in an ionic crystal are arranged in:

A systematic, periodic 3-D array

The systematic, periodic 3-D array that the cations and anions in an ionic crystal are arranged in maximizes the:

Attractive forces among cations and anions

The systematic, periodic 3-D array that the cations and anions in an ionic crystal are arranged in minimizes the:

Repulsive forces among cations and anions

Ionic solids tend to be:

Brittle

Metallic bonding can be represented as:

An array of positive metal ions surrounded by delocalized valence electrons

Delocalized valence electrons are also called:

Sea of electrons

Interstitial alloys form between:

Atoms of different radii

Where do smaller atoms go in interstitial alloys?

Interstitial spaces between the larger atoms

Which atom is the smaller one in steel?

Carbon

Which atom is the larger one in steel?

Iron

Arrangement of atoms in steel:

Carbon occupies interstices in iron

Substitutional alloys form between:

Atoms of comparable radius

What happens to atoms in substitutional alloys?

One atom substitutes for the other in the lattice

In brass alloys, what atoms substitute for what atoms?

Zinc for copper

Lewis diagrams can be constructed according to:

An established set of principles

Groups 1,2, and 13-18 are known as:

Main-group elements

The number of valence electrons for a main-group element is based on the pattern of:

Electron configurations

The term Lewis symbol (or Lewis dot symbol) refers to:

A method used to represent the valence electrons of an atom

In cases where more than one equivalent Lewis structure can be constructed, ______ must be included

Resonance

Resonance acts as a:

Refinement to the Lewis structure