Atomic Number Number of Protons

Mass Number Number of Protons + Neutrons

C-12 or carbon is the mass number.

12 C Left Superscript = mass number 6

12 C Left Subscript = atomic number 6

80 Br 35 Atomic Number = ?

20 Ne Mass Number = ?

238 U Mass Number = ?

27 Al Mass Number = ?

40 Ca 20 Atomic Number = ?

19 F 9 9 Atomic Number = ?

U-235 Mass Number = 235 Atomic Number = 92 (Look up!) Mass Number? Atomic Number?

C-14 Mass Number = 14 Atomic Number = 6 (Look up!) Number of neutrons = = 8 How many neutrons?

Isotope Atoms of the same element with a different # of neutrons

Isotope Atoms with the same atomic # but different mass #

Characteristics of Proton Charge = +1, mass = 1 amu, location = inside nucleus

Characteristics of Neutron Charge = 0, mass = 1 amu, location = inside nucleus

Characteristics of Electron Charge = -1, mass = 1/1836 amu or amu, location = outside nucleus

Ion An atom that has gained or lost electrons & so carries charge

Nucleons Protons & Neutrons

atom Smallest bit of an element that retains the properties of the element.

atom Electrically neutral. # of protons = # of electrons.

Charge # protons - # electrons

# of neutrons Mass number – atomic number

14 C 8 6 # of neutrons = ?

9 Be 5 4 # of neutrons = ?

40 Ar # of neutrons = ?

15 N 8 7 # of neutrons = ?

24 Mg Right superscript = charge 12 2+

24 Mg 10 electrons # of electrons?

86 Rb 36 electrons # of electrons?

127 Te 53 electrons # of electrons?

32 S 18 electrons # of electrons?

20 F 9 protons, 11 neutrons, 10 electrons 9 - # of protons, neutrons, electrons?

Cation Positive ion: atom lost electrons

Anion Negative ion: atom gained electrons

Avg. Atomic Mass Weighted avg. of masses of naturally occurring isotopes of an element.

2 isotopes of Cl: 75% Cl-35 & 25% Cl-37. Calculate avg. atomic mass. Avg. atomic mass =.75(35) +.25(37) = 35.5 amu

Dalton’s Model Billiard Ball Model

Thomson’s Model Plum Pudding Model

Rutherford’s Model Nuclear Model

Rutherford’s Experiment Source:

Rutherford’s Experiment: Results 1)Most of the alpha particles went straight through.  Most of the atom is empty space. 2)Some of the alpha particles were deflected back.  The nucleus was tiny, but contained most of the mass of the atom.

Bohr’s Model Planetary Model

Schrodinger’s Model Modern or Quantum Mechanical Model Source: #atomic

Modern Model (Schrodinger or Quantum Mechanical Model) Electron treated as a wave. Never know exactly where it is.

Bohr Configuration Ground state configurations found in reference tables. Cannot be predicted.

Bohr Configuration of Na = electrons in energy level 1 8 electrons in energy level 2 1 electron in energy level 3

Bohr Diagram of Na +11

Valence Electron(s) Electron(s) in outermost orbit or shell

Kernel Nucleus + all innershell electrons: Everything except the valence electrons

Bohr Model Electrons are restricted to specific orbits or shells or principle energy levels. Each shell holds a specific # of electrons. Each shell has a specific energy & radius. Energy of electron must match energy of shell.

Maximum Capacity of Bohr Levels Shell #Max # of electrons n n 2

Ground State Bohr model Every electron is in the lowest available orbit.

2-8-7 Ground state configuration of Cl

2-6 Ground state configuration of O

Ground state configuration of Kr?

Principle Energy Level? Shell #

Excited State Bohr model An electron has absorbed heat, light, or electrical energy and moved to a higher energy level. Unstable. Returns to ground state quickly by emitting a photon.

2-5-1 An excited state of O

2-0-1 An excited state of Li

Continuous Spectrum Spectrum produced by holding a prism in sunlight. Contains light at every wavelength. Rainbow

Bright Line Spectrum Visible light produced by electrons in atom returning to ground state: light of only a few wavelengths is present. Each element has a unique bright line spectrum. Used to identify elements. Wavelengths of bright lines correspond to difference between energy levels. Source:

Absorbtion of Energy h Ground state Excited state E1E1 E2E2 E3E3

Emission of Energy h Ground state Excited state E1E1 E2E2 E3E3

Orbital Modern Model Region of space that holds 2 electrons. Has a specific energy. Shapes vary.

E1E1 E2E2 Represents an electron dropping to a lower energy level, releasing energy in the process.