Chemistry

Molecular and Empirical Formulas

Shows the number of atoms in each molecule ( Ex: C(6)H(12)O(6)

Smallest integer ratios of atoms in a molecule ( Ex: CH(2)O

N(A) = 6 × 10²³ / mol

Mass of a molecule; equal to the sum of the atomic masses of all the atoms in the molecule ( Ex: 23+16+1 = 40 Da )

Basic SI unit for the amount of a substance; equal to Avogadro’s number ( 6 × 10²³ ) of particles, molecules, or ions

Mass of one mole of a compound (Ex: NaOH 40g/mol )

Molarity (M) = moles/liter = mol/L

1 atm = 10^5 Pa = 760 mmHg = 760 torr

1 L = 1000 mL = 1000 cm³

T(K) = T(C) +273

g/moles = g/mol

Percent mass of each element in a compound (Ex: HClO(4 = H = 1%, Cl = 34%, and O = 65%)

The reactant that is completely consumed when the reaction is completed and determines the amount of product that can be formed

The maximum amount of product that can be formed and the actual yield is always lower than the theoretical yield

Actual Yield / Theoretical Yield

Code for an element (Ex: C = Carbon)

Z = Number of protons = nuclear charge and uniquely identifies the element

A = Number of protons + neutrons

Atoms with the same number of protons but different number of neutrons

C = protons - electrons

Atoms with nonzero charge

Charge > 0

Charge < 0

Repulsive force between the positively charged protons

An attractive force between protons and electrons

The mass of a nucleus is less than the sum of the masses of the individual protons and neutrons and the loss of mass results in a release of energy

Amount of energy required to separate a nucleus into individual protons and neutrons (always a positive value). Different atoms have different amounts of nuclear binding energy per proton/neutron. In nuclear reactions, energy is released if the products have greater nuclear binding energy than the reactants.

Combining nuclei to form heavier nuclei

Describes splitting nuclei into lighter nuclei.

Have unstable nuclei

The process by which an unstable nucleus emits radiation (alpha, beta, or gamma) to form a more stable nucleus

The nucleus emits an alpha particle (Two protons and two neutrons) A decreases by 4 and Z decreases by 2. Occurs with massive nuclei. A and Z must be balanced on both sides of the reaction.

The nucleus emits an electron n → p + e- . A stays the same, Z increases by 1 and occurs with nuclei with a high neutron to proton ratio.

The nucleus emits a positron n → p + e+ . A stays the same, Z decreases by one, and occurs with nuclei with a low neutron to proton ratio

The nucleus absorbs an electron. p + e- → n . A stays the same, Z decreases by one, and occurs with nuclei with a low neutron to proton ratio

The nucleus emits a gamma ray. A and Z stays the same. Occurs with nuclei in an excited state.

Occurs when a quantity decreases at a rate proportional to its current amount

The amount of time required for a substance to decay to half of its initial quantity

A model of the atom where electrons follow circular orbits (called energy levels/shells) located at fixed distances away from the nucleus

Increase in energy away from the nucleus, have energies that are quantized, and get progressively closer together away from the nucleus

Indicates the energy level/shell

Electrons can move from a lower energy level/shell to a higher energy level/shell by absorbing a photon (ground state to an excited state). The photon must have an energy equal to the difference in energy between the two levels.

Electrons in the excited state will spontaneously move from a higher energy level/shell to a lower energy level/shell by emitting a photon. The emitted photon has an energy equal to the difference in energy between the two levels.

E = hv, E is= energy of a photon, v = frequency, and h = planck’s constant (6.6 × 10^-34 J/s)

E = hc/lamda, lamda = wavelength, c = speed of light in a vacuum (3 × 10^8 m/s), and h = planck’s constant (6.6 × 10^-34 J/s)

A continuous spectrum contains light of all wavelengths (Ex: White light)

Contains light at only discrete wavelengths (bands)

White light is shined onto a sample in its ground state. The sample absorbs some wavelengths of light. The unabsorbed light is passed through a prism to produce the absorption spectrum.

Indicate which wavelengths of light were absorbed by the sample

A sample in its excited state emits light that is passed through a prism to produce the emission spectrum

Indicate which wavelengths of light were emitted by the sample

Light and matter behave like both particles and waves

Passed light through a screen with two slits, if light was a particle then the viewing screen should only show two bright lines but instead a pattern of bright and dark bonds that were the result of wave diffraction and interference appeared, so light exhibits wave behaviors

Emission of photoelectrons from metal when shined with light and ejection of photoelectrons depended only on the frequency of light and not on the intensity, so light exhibits particle behavior

The amount of energy required to eject an electron from a metal

It is impossible to accurately measure both the position and momentum of a particle simultaneously, the more precisely one is measured the more uncertainty there is for the other

Electrons reside in atomic orbitals that can be described by: Size/Energy = Energy Level/Shell, Shape = Subshell, Electron Spin = Up or Down

The size of an orbital is determined by the energy level/shell which is indicated by the principle quantum number (n)

Quantized energies, increase in energy away from the nucleus, and get progressively closer together away from the nucleus

Determined by the subshell

The blocks on the periodic table

1 spherical orbital

3 dumbell orbitals

5 orbitals

7 orbitals

Each orbital can only fit two electrons and they must have opposite spin (up or down)

A notation used to represent the distribution of electrons in an atom in its ground state and electrons fill orbitals from lowest to highest energy

In the Bohr Model, electrons are depicted as orbiting the nucleus in fixed circular paths, while the Quantum Mechanical Model describes the electron's location in terms of its probability distribution or electron cloud, based on its wave-like nature.

Electrons are removed from electrons in the valence (outermost) shell orbitals from highest to lowest energy

An element's electron configuration can be shorthand represented by enclosing the preceding noble gas in brackets and writing the remaining configuration for the outer electron shells

Electrons fill degenerate orbitals (orbitals in the same subshell) one per orbital before pairing

Unusually stable and elements in the 4th and 9th columns of the d block will move an electron from the s orbital to the d orbital to attain the unusual stability

Not all electrons are paired

All electrons are paired

Elements are organized by atomic number and recurring patterns of chemical properties. Elements in the same group (column) have the same number of valence electrons and similar chemical properties

Elements in the last column of the periodic table, have a full valence shell and very low chemical reactivity (inert), are monatomic, and exist in the gas phase at standard conditions due to having very weak intermolecular forces

Elements in the second to last column of the periodic table, are very reactive due to high electronegativity, have 7 valence electrons, and can gain one electron to attain noble gas configuration . Diatomic elements and exist in different phases at standard conditions.

The elements in the third to last column of the periodic table. They have 6 valence electrons and need to gain 2 electrons to attain noble gas configuration.

The elements in the first column of the periodic table, are very reactive, and only lose their only valence electron to attain noble gas configuration

The elements in the second column of the periodic table and these elements lose their two valence electrons to attain noble gas configuration

The elements in the s and p blocks of the periodic table and are the most abundant elements on earth

The elements in the d block of the periodic table and are the source of color in many colored compounds

F(E) = k Q(1)Q(2) / r

Electrons in an atom experience an attractive electrostatic force from the positive nuclear charge (z)

Electrons in the outermost shell of the atom; participate in chemical bonds and reactions

All nonvalence electrons; valence electrons do not feel the full positive charge of the nucleus because of the shielding provided by them

F(E) is proportional to e x Z(eff) / r²

Charge of an electron

Effective nuclear charge = p+ - # of core e- ; does not change along a column, the distance between the nucleus and valence electrons increases moving down a column, as electrons are added to larger shells that are farther from the nucleu

Distance between the nucleus and the valence shell

The size of an atom’s electron cloud

Increases due to the Z(eff) effective nuclear charge increasing too

Decreases due to r (distance between the nucleus and the valence shell) increasing

Inversely related to the electrostatic force

Radius decreases due to electrostatic force increasing

Radius increases due to electrostatic force decreasing

Addition of electrons increases the radius

Removal of electrons decrease the radius

The amount of energy required to remove an electron from an atom or ion; proportional to electrostatic force