College Chemistry Ch 2

The structure of the atom and the periodic table

Atom

the basic unit of a chemical element.

Nucleus

Small, dense, positively charged region in the center of the atom containing protons and neutrons

Proton

Positively charged particles

Neutron

Uncharged particles

Electron

Negatively charged particles, located outside of the nucleus of an atom

Atomic number (Z)

The number of protons in an atom

Mass number (A)

Some of the number of protons and neutrons

Isotopes

Atoms of the same element having different masses

Dalton's atomic theory

The first experimentally based theory of atomic structure

Cathode Ray

a stream of electrons produced at the negative electrode of a tube containing a gas at low pressure

Gold foil experiment

Conducted by Ernest Rutherford in which alpha particles that were shot at gold foil were deflected when they hit the positive center of gold atoms. The nucleus was discovered as a result of this experiment.

Spectroscopy

The study of the properties of light that depend on wavelength.

Electromagnetic radiation

a kind of radiation including visible light, radio waves, gamma rays, and X-rays, in which electric and magnetic fields vary simultaneously.

Speed of light

3.00 x 10^8 m/s

Wavelength

Horizontal distance between the crests or between the troughs of two adjacent waves

Electromagnetic spectrum

the range of wavelengths or frequencies over which electromagnetic radiation extends.

Orbit

Fixed energy levels

Ground state

The lowest energy state of an atom

Periodic law

the physical and chemical properties of the elements are periodic functions of their atomic numbers

Period

A horizontal row of elements in the periodic table

Group

A vertical column in the periodic table, also known as a family of elements

Metal

Elements that tend to lose electrons during chemical change, forming positive ions

Nonmetal

Elements that tend to gain electrons during chemical change, forming negative ions

Metalloid

an element that has properties of both metals and nonmetals

Electron configuration

the arrangement of electrons in an atom

Valence electrons

Electrons on the outermost energy level of an atom

Sublevel

A set of energy equal orbitals within a principal energy level

Atomic orbital

A specific region of a sublevel, containing a maximum of two electrons

Orbital shapes

s (spherical); p (dumbbell); d (double dumbbell plus donut); f (too complicated)

Aufbau Principle

states that each electron occupies the lowest energy orbital available (s,p,d,f)

Pauli Exclusion Principle

states that a maximum of two electrons can occupy a single atomic orbital but only if the electrons have opposite spins

Hund's Rule

orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin

Octet rule

atoms react by gaining or losing electrons so as to acquire the stable electron structure of a noble gas, usually eight valence electrons

Ions

Electrically charged particles that result from a gain or loss of one or more electrons by the parent atom

Cation

A positively charged ion

Anion

A negatively charged ion

Cation size

smaller than parent atom

Anion size

larger than parent atom

Ionization energy

Energy required to remove an electron from an isolated atom

Electron affinity

Energy released when a single electron is added to an isolated atom