Unit 2: Atomic and Electronic Structures 1.2, 1.3, 3.1

Nucleus

Very small very dense, positively charged

nucleons

protons and neutrons

electron cloud

vast area outside of nucleus occupied by electrons

isotopes

elements with the same number of protons, but with different numbers of neutrons (different mass numbers)

• have the same chemical characteristics

• different physical characteristics (aka boiling point, melting point)

ions

a charged particle (with either extra or missing electrons)

Cation

• positively charged

• looses electrons

Anions

• negatively charged

• gains electrons

Relative atomic mass

weighted average based on the relative mass of a nucleon

finding relative atomic mass

A= sum (isotope mass * percent abundance)

E=hf=(hc)/wavelegth

E= energy in joules

H= planks constant 6.63×10^-34 JS

F= frequency 1/s

C = 3.00×10^8 m/s

Ultraviolet light

anything to the 1st energy level

Visible light

anything to 2nd energy level

Infared (IR)

anything to 3rd energy level

ionization energy

the energy required to remove one electron from a atom

Aufbau principle

electrons must ocupy orbitals of the lowest energy first

Hunds Rule

first add one electron to sublevel before doubling up

Pauli exclusion principle

must have opposite spins

Emission spectrum

pure gaseous elements subjected to high volumes and decreased pressure, creates a series of lines against a dark black background

Continuous spectrum

results from the breaking of light, contains light of all wavelengths together

Absorption Spectrum

cold gas, series of dark lines with a continuous spectrum