General Chemistry Exam 1 Vocabulary

Atom

The smallest particle of an element that cannot be chemically or mechanically divided into smaller particles

Element

A pure substance that cannot be separated into simpler substance

Compound

A pure substance composed of two or more elements that are chemically bonded in fixed proportion

Matter

Anything that has mass or occupies space

Mixture

Combination of pure substances in various proportions in which the individual substances retain their chemical identities and can be separated from one another by a physical process

Homogeneous mixture

Mixture in which the components are distributed uniformly

Heterogeneous mixture

Mixture in which the components are not distributed uniformly

Chemical properties

Those that can be observed only by reacting the substance with something else to form another substance

Physical properties

Those that can be observed without changing the substance into another substance

Intensive properties

Independent of the amount of the substance

Extensive properties

Dependent on the amount of a subatance

Physical process (physical change)

A transformation of a sample of matter, such as a change in its physical state, that does not alter the chemical identity of any substance in the sample

Chemical reaction (chemical change)

The conversation of one or more substance or negative charge

Ion

A particle consisting of one or more atoms that has a net positive or negative charge

Density

The ratio of the mass (m) of a substance or object to its volume (v)

Sublimination

Transformation from solid to gas, energy absorbed

Deposition

Transformation from vapor to solid, energy released

Melting

Transformation from solid to liquid, energy absorbed

Freezing (fusion)

Transformation from liquid to solid, energy released

Condensation

Transformation of gas to liquid, energy released

Vaporization

Transformation of liquid to gas, energy absorbed

Energy

The capacity to do work

Potential energy

The energy stored in an object because of its position or composition

Kinetic energy

The energy of motion

Precision

Based upon the reproductivity of a measurement or the agreement between values

Accuracy

How close a measured value is to the true value

Significant figures

All the certain digits in a measured value plus one estimated digit. The greater the number of significant figures, the greater the certainty with which the value is known

Standard deviation

A measure of the amount of variation, or dispersion, in a series of related values

Atomic number (Z)

The number of protons in the nucleus

Mass number (A)

The total number of protons and neutrons

Electron

Negatively charged sub-atomic particle

Proton

Positively charged sub-atomic particle

Neutron

Neutrally charged sub-atomic particle

Cation

Positively charged ion due to loss of electrons

Anion

Negatively charged ion due to gain of electrons

Isotopes

Atoms of an element containing the same numbers of protons but different numbers of neutrons

Periods

Horizontal rows (1-7)

Groups

Vertical columns (1-18); also knows as families

Molecular mass

The sum of all the average atomic masses of the atoms that are chemically bonded together

Molar mass

The mass (in grams) of one mole of a substance (atom, molecule, or formula unit)

Wavelength (lambda)

The distance from one wave crest to another

Frequency (nu)

the number of crests that pass a stationary point per second. Hertz (Hz) is the unit meaning “per second”)

Quantized (values)

Restricted to whole-number multiples of a specific base value

The photoelectric effect

Electrons are emitted from a metal surface when it is illuminated by and absorbs electromagnetic radiation that exceeds the threshold frequency (V0)

Emission

Energy leaves

Absorption

Energy gained

Quantum (of energy)

The smallest quantity of energy that can be emitted (or absorbed)

Heisenberg uncertainty principle

It’s impossible to know simultaneously both the momentum (p) and the position (x) of a particle with certainty

Electron density

The probability of finding an electron in a certain area of space is proportional to the probability density

Atomic orbital

The area of high probability of finding any electron of an atom around the atom’s nucleus

Orbitals

3-dimensional regions in the atoms where the probability of finding an electron is high

The Schrodinger equation

Specifies possible energy states of an electron

Quantum numbers

Describe atomic orbitals which define the energy and shape of high probability

Principal quantum number (n)

Positive integer describing the relative size and energy of an atomic orbital

Angular momentum quantum number (l)

Integer having any value from 0 to n-1 that defines the shape of an orbital and contributes to the energy

Magnetic quantum number (m_l)

Defines the orientation of an orbital in space. An integer that many have any value from -l to +l, where l is the angular momentum quantum number

Spin quantum number (m_s)

Either +1/2 or -1/2; indicating the spin orientation of an electron within an orbital

Shell

A collection of orbitals with same value of n

Subshell

A collection of orbitals with the same value of n and e

Electron configuration

Describes how the electrons are distributed in various atomic orbitals

Pauli exclusion principle

No 2 electrons in an atom can have the same 4 quantum numbers

Aufbau principal

Electrons are added to lowest energy orbitals first before moving to high energy orbitals

Hund’s rule

The most stable arrangement of electrons is the one in which the number of electrons with the same spin is maximized

Degenerate

Of equal energy

Diamagnetic

When all electrons in an atom are paired, as in neon

Paramagnetic

When an atom contains an unpaired electron, as in carbon

Valence electrons

The outermost electrons in an atom. Only electrons associated with the highest principal quantum number

Isoelectronic

Species with the same electron configuration

Main group elements

Elements in the s and p block

Effective nuclear charge (Z_eff)

the actual magnitude of positive charge that is “experienced” by an individual electron in the atom

Shielding

When an electron is partially shielded from the positive charge of the nucleus by the other electrons