Chemistry Exam 1 Terms/Formulas

NOT A COMPREHENSIVE REVIEW!!! JUST THINGS WE SHOULD HAVE MEMORIZED

giga-

10^9

mega-

10^6

kilo-

10^3

hecto-

10^2

deka-

10^1

deci-

10^-1

centi-

10^-2

milli-

10^-3

micro-

10^-6

nano-

10^-9

pico-

10^-12

femto-

10^-15

Quantized

When a property can only exist in discrete levels, as opposed to in a spectrum. For example, photons carry quantized amounts of energy.

Potential Energy

Energy possessed by an object because of its state/position. An electron has high potential energy farther from the nucleus and lower potential energy closer to the nucleus.

Kinetic energy

Energy that comes from the actual motion of an object. Electrons close to the nucleus have high kinetic energy but low potential energy.

Photoelectric Effect

When a metal plate is hit with light/radiation with a sufficient frequency, it will eject electrons.

Threshold Frequency

The minimum frequency needed to eject one electron.

Energy of a photon

E = hv

Constructive Interference

When two waves that are in sync collide, they will create a larger wave.

Destructive interference

When two waves that are out of sync collide, they will cancel out.

Orbit

Fixed rotational patterns around the nucleus, used in the Bohr Model. Implies that we know exactly where an electron is and how it moves.

Orbital

A mathematical function that describes a 3D area around the nucleus where there’s a high chance (~90%) of finding an electron. (3-D region around the nucleus within a shell that represents a different orientation of a subshell that may contain an electron (~90%).) We don’t know exactly where the electron is (uncertainty). Orientation described by the orbital/magnetic quantum number ml.

Degenerate Orbital

Orbitals with the same energy.

Radial node

Spherical plane where the probability of finding an electron is zero. Number of radial nodes can be found using n-l-1= # of radial nodes.

Planar nodes

Flat planes where the probability of finding an electron is zero. Defined by quantum number l.

Paramagnetic

When an atom has one or unpaired electrons (in the context of atomic orbitals).

Diamagnetic

When all of the electrons in an atom's orbitals are paired.

Pauli's exclusion principle

No two electrons with the same spin/ same four quantum numbers can exist in the same orbital. If they do, it implies that they exist in the same place at the same time (spin is defined by electron spin quantum number ms).

Aufbau's Rule

Electrons will fill lower energy orbitals before filling higher energy orbitals.

Hund's rule

Electrons within a subshell will occupy orbitals individually before pairing. Unpaired electrons will have the same spin as each other.

Condensed electron configuration

Noble gas electron configuration.

Shell

Regions with discrete energy levels that surround the nucleus and house subshells/electrons. Synonymous with "energy level” and are defined by the principle quantum number, n.

Subshell

3D region within a shell that house electrons. Have a shape defined by the orbital angular momentum quantum number l.

Extensive properties

Properties that depend on the amount of matter present such as mass, weight.

Intensive properties.

Properties that only depend on the type of matter, such as conductivity and melting point.

Atomic number

How many protons are in the nucleus of an atom of an element.

Atomic mass

The number of protons and neutrons in the nucleus of an atom.

Average atomic mass

The average mass of an element based on the percent distributions of its naturally occurring isotopes. Measured in amu, and measures mass of a single atom.

Wave - particle duality

This term describes the nature of electrons and light/photons, as they exist as both waves and particles at the same time.

Wavelength (lambda)

The distance between two identical points on a wave. Inversely . proportional to both energy and frequency

Frequency (v or f)

How often a wave passes through a given point in one second. Directly related to energy, inversely related to wavelength.

Amplitude

Distance between the midline and the peak/ trough of a wave. Proportional to energy in that energy= amplitude squared. No relation to frequency.

Intensity

The number of photons in a wave. No relation to energy.

Law of conservation of energy

Energy cannot be created or destroyed (why when we have high potential energy, we have low kinetic + vice versa).