Chapter 4 Chemistry

electromagnetic radiation

a form of energy that exhibits wavelike behavior as it travels through space

electromagnetic spectrum

all the forms of electromagnetic radiation

Wavelength

the distance between corresponding points or adjacent waves

frequency

the number of waves that pass a given point in a specific time, usually one second

photoelectric effect

the emission of electrons from a metal when light shines on the metal

quantum

the minimum quantity of energy that can be lost or gained by an atom

Max Planck

physicist who proposed relationship between a quantum of energy and frequency of radiation. E=hv

photon

a particle of electromagnetic radiation having zero mass and carrying a quantum of energy

ground state

the lowest energy state of an atom

excited state

a state in which an atom has a higher potential energy than it has in its ground state

line-emission spectrum

the four bands of light were part of what is known as hydrogen’s

Niels Bohr

proposed a hydrogen-atom model that linked the atom’s electron to photon emission

orbits

allowed paths that electrons can circle around the nucleus

emission

when an electron falls to a lower energy level, a photon is emitted

absorption

energy added to an atom to move an electron from a lower energy level to a higher energy level

diffraction

the bending of a wave as it passes by the edge of an object or through a small opening

interference

this occurs when waves overlap

Heisenberg uncertainty principle

states that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle

Quantum theory

describes mathematically the waves properties of electrons and other small particles

orbital

a three-dimensional region around the nucleus that indicates the probable location of an electron

Quantum numbers

specify the properties of atomic orbitals and the properties of electrons in orbitals

principal quantum number

symbolized by n; indicates the main energy level occupied by the electron; n=1-7

angular momentum quantum number

symbolized by l; indicates the shape of the orbital; l=0-n-1

magnetic quantum number

symbolized by m; indicates the orientation of an orbital around the nucleus; m=-l-l

Spin Quantum Number

½ or -1/2; indicates two fundamental spin states of an electron in an orbital

Shapes of groups

s=sphere p=dumbbell d=two dumbbells

electron configuration

the arrangement of electrons in an atom

ground-state electron configuration

the lowest-energy arrangement of the electrons for each element

Aufbau Principle

an electron occupies the lowest-energy orbital that can receive it

Pauli exclusion principle

no two electrons in the same atom can have the same set of four quantum numbers

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 states

Noble gases

the group 18 elements