GenChem 1 Midterm Exam Review

Molecular Formula

The actual number of atoms of each element that make up a molecule.

Empirical Formula

The lowest whole-number ratio of atoms of each element that make up a molecule.

Mole

The amount of substance containing the same number of atoms, molecules, ions, or other entities as the number of atoms in exactly $12\text{ grams}$ of $^{12}\text{C}$.

Avogadro’s Number

The number of entities in a mole, equal to $6.022 \times 10^{23}$.

Molar Mass

Also referred to as Molecular Mass, Molecular Weight, or Formula Mass; the mass of one mole of an element or substance, calculated using the average mass of each element as reported on the periodic table.

Percent Composition

The percentage by mass of each element in a compound.

Percent Composition of an Element in a Compound (Equation)

$$\text{\% Composition} = \frac{\text{mass of element in compound}}{\text{mass of compound}} \times 100\%$$

Number of Units in Molecular Formula (Equation)

$$\text{\# of units in Molecular Formula} = \frac{\text{Molecular Formula Mass}}{\text{Empirical Formula Mass}}$$

Chemical Equation

A symbolic representation of a chemical reaction that shows the chemical formulas of the species involved in the reaction.

Reactant

A substance undergoing a chemical or physical change; it is written on the left side of the arrow in a chemical equation.

Product

A substance formed by a chemical or physical change; it is written on the right side of the arrow in a chemical equation.

Coefficient

The number placed in front of symbols or formulas in a chemical equation to indicate their relative amount.

Molar Ratio

The ratio of coefficients of two substances in a chemical equation.

Balanced Equation

A chemical equation with equal numbers of atoms for each element in the reactant and product.

Stoichiometry

The study of the quantitative relationships or ratios between two or more substances undergoing a physical change or chemical change.

Limiting Reagent

The reactant present in a molar amount lower than required by the reaction stoichiometry, which limits the amount of product that can be formed.

Theoretical Yield

The amount of product that may be produced from a given amount of reactant(s) according to the reaction stoichiometry.

Actual Yield

The actual amount of product reported to be produced experimentally.

Percent Yield

The measure of the efficiency of a reaction, expressed as a percentage of the theoretical yield.

Percent Yield of a Reaction (Equation)

$$\text{\% Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100\%$$

Principle Quantum Number (n)

Defines the shell, primary energy level, and size of orbital

Angular Momentum Quantum Number (l)

Defines the sub shell and geometric shape of the orbital

Pauli Exclusion Principle

An orbital can hold a maximum of two electrons of opposite spin

Aufbau Principle

Electrons fill sub shells in order of increasing energy

Hund’s Rule

Every orbital in a sub shell is filled with one electron before being filled with a second electron

Effective Nuclear Charge Definition

The net positive charge pulling a valance electron

Effective Nuclear Charge Trend

Increases left to right across the periodic table

Covalent Radius Trend

Increases down a group (column), and decreases left to right

Ionic Radius

Cations are significantly smaller than parent neutral atoms

Ionization Energy (IE) Definition

The energy required to remove the most loosely bound electron from an atom in its ground state

Ionization Energy (IE) Trend

Increases across, decreases down a group

Core electrons require ______ ionization energy, in comparison to valance electrons

higher

Electron Affinity (EA) Definition

Energy change when an electron is added to an atom

Electron Affinity (EA) Trend

Becomes more negative left to right

Ionic Bonding

Attraction between oppositely charged ions resulting in electron transfer; between metals and non-metals

Covalent Bonding

Attraction between atoms resulting from the sharing of electrons; typically occurs between non-metals.

Electronegativity (EN)

Measures the tendency of an atom in a molecule to attract bonding electrons

Pure (nonpolar) covalent Electronegativity

~0

Polar Covalent Electronegativity

0.1-1.9

Ionic Electronegativity

Greater than 2.0

Resonance Lewis Structures

Represent the same molecule with different arrangements of electrons

Formal Charge Equation

Valance electrons - unshared electrons - ½ bonding electrons

Chemistry

the study of matter and its properties, the changes matter undergoes, and the energy associated with those changes

Matter

anything that occupies space and has mass; “stuff”

Forms of Matter

solid, liquid, gas

Solid

a condensed state of matter that is rigid, has a definite shape, with particles packed closely in an organized manner

Liquid

a condensed state of matter that conforms to a container’s shape, but only to the extent of its own volume, with particles that are close together but disorganized

Gas

an expanded state of matter that conforms to a container’s shape completely, with particles that are far apart and disorganized

Physical Properties

a characteristic of matter not associated with any change in its chemical composition

Chemical Properties

a characteristic of matter associated with interactions with other matter

Physical Change

a change in the state or properties of matter that does not involve a change in its chemical composition

Chemical Change

a change that produces a different kind of matter from the original; a chemical reaction

Atom

the smallest unit of an element that can participate in chemical change

Nucleus

the positively charged center of an atom that contains protons and neutrons, most of the atom’s mass

Proton (p+)

A positively charged subatomic particle found in the nucleus of an atom

Neutron (n0)

A neutral subatomic particle found in the nucleus of an atom

Electron (e-)

A negatively charged subatomic particle that orbits the nucleus of an atom

Law of Constant Composition

all samples of a pure compound contain the same elements in the same proportions by mass

Atomic Number

the number of protons in the nucleus of an atom; defines the element

Mass Number

the total number of protons and neutrons in an atom

Isotopes

atoms that contain the same number of protons but a different number of neutrons

Fractional Abundance

the relative amount of one isotope expressed as a decimal

Percent Abundance

the relative amount of one isotope expressed as a percentage

Atomic Mass Unit (amu)

a very small unit of mass defined as 1/12 the mass of a carbon-12 atom

Average Mass of an Element Equation

Average mass = Σ(fractional abundance of each isotope * isotopic mass)

Electrons are located in?

Specific quantized energy states

What subatomic particles has both particle and wave properties?

Electrons

What is the space where electrons have the probability of being located?

Orbitals

What do lower n-values mean?

the electrons are closer to the nucleus and the lower energy the orbital is

High energy shells are _______ from the nucleus

further

Orbital shapes

s, p, d, f

Shell shape of n=1:

s

Shells of n=2:

s and p

Shells of n=3:

s, p, d

Shells of n=4:

s, p, d, f

Pauli Exclusion Principle

Each orbital can hold 2 electrons

Aufbau Principle

electrons fill orbitals from the lowest energy up.

Hund’s Rule

electrons fill the lowest level first

Atomic Size Trend Rows

Left = largest, Right = smallest

Atomic Size Trend Columns

Top = smallest, Bottom = largest

Electrons are repelled ___ by the protons but repel each other slightly

more

Cations have ___ electrons than protons, and have an overall __ charge.

less, positive

Anions have ____ electrons than protons, have an overall ___ charge.

more, negative

Cations are always _______ than their parent atom.

smaller

Anions are always ______ than their parent atom.

larger

In cations each electron remaining, feels _____ pull by protons in nucleus.

greater

In anions each extra electron feels ____ overall pull by protons in the nucleus.

less

Ion size can only be compared if

there is a constant

What is required for a isoelectronic series

electrons to be the same, but with different number of protons

What is ionization energy?

energy required to remove electrons from an atom

Increase in ionization energy for ______ atoms

smaller

Atom size increases while ionization energy ______.

increases

In Ionization energy each takes ___ energy than the one before it.

more

In ionization energy a massive jump in energy is required after __________.

valance electrons

What is electron affinity?

the energy change when adding an electron to an atom

Electron affinity in noble gases does/does’t require energy?

Does

Electron affinity in all other main groups energy is ______.

released

In election affinity halogens ______ the most energy.

release

Ionic Bonds

the loss or gain of an electron to form charged ions

An ionic bond is always between a ______ and a ______.

metal and non-metal