CHEM Chapter 2&3 Vocab Terms

Atomic Number

• the # of protons in the nucleus of an atom (Z)

• its value determines the identity of the atom

• 6= atomic number

• atomic number (Z) indicates # of electrons too

Mass Number

• the # of protons + the #neutrons 

• the mass number is not on the period table 

Atomic Symbol

• the element symbol from the periodic table 

• EX: C for carbon, Cl for Chlorine, etc. 

Isotopes 

• atoms that have the same # of protons but different # of neutrons -

• same atomic number but different mass number 

• versions of the same element

Cation

• positively charged ion

• loses an electron

Anion

• negatively charged ion

• gains an electron 

Visible Light

Electromagnetic Radiation

Frequency

• “v”

• Hertz= 1/s

• Radiation w/ high frequency = short wavelength

• Radiation w/ low frequency= long wavelength

• Directly proportional to energy

• inversely proportional to wavelength

Wavelength

• upside down “v”

• m=units

• inversely proportional to radiation & energy

Speed of Light

• 3.00 × 10^8

• m/s

• constant (always this same equation)

Quantum Theory

• developed by Max Planck (1900)

• the energy of a small particle is quantized: it occurs in fixed quantities rather than being continuous 

• Each fixed quantity of energy (packet) is called a photon

• E=hv

Energy

• E= energy of photon

• J (joules)

• Directly proportional to Radiation

• Inversely proportional to wavelength 

Planck’s Constant

• h

• 6.626 × 10^-34 J (x) s

The Bohr Model

• Niels (1913)

• addressed gaps of “early atomic model”

• electrons occupy specific orbits around nucleus (each corresponds to a fixed energy level)

• Electrons can jump between energy levels, BUT cannot exist between them

• His wife contributed greatly to this theory, Margrethe

Quantum Staircase

• lowest energy orbit (n=1) is the GROUND STATE

• every other orbit is called EXCITED STATES (n=2 and so on)

• Moves from LOW to HIGH orbit, electron absorbs a photon

• Moves from HIGH to LOW orbit, electron emits a photon

Atomic Orbitals (wave-function)

• a 3D standing wave that describes where an electron is most-likely to be found & its associated energy 

• 3 specific quantum numbers 

  • size

  • shape

  • orientation

Principal Quantum Number

• n

• describes the energy level & general size of the orbital

• the number in orbital notation

• Larger numbers= higher energy & farther from nucleus 

Angular Quantum Number 

• l

• describes the shape of the orbital region where electron is most-likely to be found

• s= spherical

• p=dumbell

• d/f= more complex

• written as the letter in orbital notation 

Magnetic Quantum Number

• m

• describes the orientation of orbital in 3D space

• each unique orientation is written as a unique subscript

• written as z in orbital notation

Shells 

• n

• energy value

Subshells

• n + l

• a specific shape & size 

Orbital

• n + l + m

• specific shape, size, & orientation

Wavelength Ranking (shortest to longest)

gamma ray< x-ray< ultraviolet< Visible< infrared< Microwave< Radio Wave

Frequency Ranking (smallest to largest)

radio wave< microwave< Infrared< visible< ultraviolet< x-ray< gamma ray

Blackbody Radiation

when a solid object is heated to high temps it gives off electromagnetic radiation

• incandescent lightbulb

Photoelectric Effect

when sufficient frequencies of light shines on a metal plate, a current flows

• solar panels

Atomic Emission

when atoms are excited by energy they admit radiation w/discrete wavelengths not in a continuous spectrum

• neon signs

Atomic Mass

• the weighted average of all the masses of isotopes present in a natural sample

• approximately equal to and individual isotope/element’s mass number 

• weighted average is reported on the periodic table 

Molar mass

mass of 1 gram of substance per mol

g/mol

Molecular Mass

sum of the atomic masses of each element in a formula

amu