Chemistry Final Review

Macroscopic domain

Everyday things that are large enough to be sensed directly by human sight or touch. The macroscopic domain includes everyday and laboratory chemistry, where we observe and measure physical and chemical properties such as density, solubility, and flammability.

Microscopic domain

Often visited in the imagination. Some aspects of the microscopic domain are visible through standard optical microscopes, but some things are far too small to see.

Symbolic domain

Specialized language used to represent components of the macroscopic and microscopic domains. Chemical symbols (such as those used in the periodic table), chemical formulas, and chemical equations are part of the symbolic domain, as are graphs, drawings, and calculations.

Scientific Notation

• A number larger than one will have a positive exponent.

• A number smaller than one will have a negative exponent.

Uncertainty

Estimate of amount by which measurement differs from true value

Significant Figures

All of the digits in a measurement, including the uncertain last digit

Significant Figure Rule for Subtraction and Addition

When we add or subtract numbers, we should round the result to the same number of decimal places as the number with the least number of decimal places (the least precise value in terms of addition and subtraction)

Significant Figure Rule for Multiplication and Division

When we multiply or divide numbers, we should round the result to the same number of digits as the number with the least number of significant figures (the least precise value in terms of multiplication and division).

Mass

Measure of the amount of matter in it

Law of conservation of matter

There is no detectable change in the total quantity of matter present when matter converts from one type to another (a chemical change) or changes among solid, liquid, or gaseous states (a physical change).

Pure substance

Has a constant composition. All specimens of a pure substance have exactly the same makeup and properties.

Element

Pure substances that cannot be broken down into simpler substances by chemical changes

Compounds

Pure substances that are comprised of two or more elements. Compounds may be broken down by chemical changes to yield either elements or other compounds, or both

Mixture

Composed of two or more types of matter that can be present in varying amounts and can be separated by physical changes

Homogeneous mixture/Solution

Exhibits a uniform composition and appears visually the same throughout

Heterogeneous mixture

A mixture that is not completely uniform in composition, varying from point to point

Physical property

A characteristic of matter that is not associated with a change in its chemical composition. Familiar examples of physical properties include density, color, hardness, melting and boiling points, and electrical conductivity.

Physical change

A change in the state or properties of matter without any accompanying change in the chemical identities of the substances contained in the matter. Physical changes are observed when wax melts, when sugar dissolves in coffee, and when steam condenses into liquid water.

Chemical property

The change of one type of matter into another type (or the inability to change). Examples of chemical properties include flammability, toxicity, acidity, and many other types of reactivity

Chemical change

Always produces one or more types of matter that differ from the matter present before the change

Extensive property

Property depends on the amount of matter present. The value of an extensive property is directly proportional to the amount of matter in question

Intensive property

Property of a sample of matter does not depend on the amount of matter present.

Isotopes

Atoms of the same element that differ in mass

Atomic number (Z)

The number of protons in the nucleus of an atom. The atomic number is the defining trait of an element: Its value determines the identity of the atom.

Number of Electrons

A neutral atom must contain the same number of positive and negative charges, so the atomic number also indicates the number of electrons in an atom.

Mass Number (A)

The total number of protons and neutrons in an atom

Number of Neutrons

The difference between the mass number and the atomic number: A – Z = number of neutrons

Atomic charge

Atomic charge = Number of protons - number of electrons

Bohr Model

Showed the hydrogen atom electron’s energy decreases with increasing distance from the nucleus

Principal quantum number

n, defines the general size and energy of the orbital. Another name for the principal quantum number is the shell number

Shells

The shells of an atom can be thought of as concentric spheres radiating out from the nucleus. The electrons that belong to a specific shell are most likely to be found within the corresponding spherical area. The further we proceed from the nucleus, the higher the shell number, and so the higher the energy level.

Atomic orbital

is a general region in an atom within which an electron is most probable to reside.

Secondary (angular momentum) quantum number (l)

l specifies the shape of the orbital

• It is an integer that may take the values, l = 0, 1, 2, …, n – 1. The highest possible value of l is one less than the principal quantum number.

• This means that an orbital with n = 1 can have only one value of l, l = 0, whereas n = 2 permits l = 0 and l = 1, and so on

S Orbitals

They make up the s subshells. l = 0

P orbitals

l=1

D orbitals

The orbitals with l = 2

F Orbitals

l = 3

Magnetic quantum number m_l

Specifies the relative spatial orientation of a particular orbital

• Generally speaking, m_l can equal all integers from –l to +l. The total number of possible orbitals with the same value of l (that is, in the same subshell) is 2l + 1.

Spin quantum number m_s

Specifies the orientation of the spin of an electron

• m_s can only have a value of +1/2 or -1/2

Pauli exclusion principle

No two electrons in the same atom can have exactly the same set of all the four quantum numbers.

• No more than two electrons can occupy the same orbital 2n² (and if two electrons are located in the same orbital, they must have opposite spins)

The Aufbau Principle

Each added electron occupies the subshell of lowest energy available, subject to the limitations imposed by the allowed quantum numbers according to the Pauli exclusion principle. Electrons enter higher-energy subshells only after lower-energy subshells have been filled to capacity.

Hund's Rule

When you're filling orbitals of the same energy, electrons spread out before pairing.

C = 1s² 2s² 2p²

The 2p orbitals are:

↑ ↑ _

NOT:

↑↓ _ _

Hund's rule says the lowest-energy arrangement has the maximum number of unpaired electrons.

Electron Configuration Table

This partial periodic table shows electron configurations for the valence subshells of atoms. By “building up” from hydrogen, this table can be used to determine the electron configuration for atoms of most elements in the periodic table.