Atomic Number Number of Protons
Mass Number Number of Protons + Neutrons
12 C Left Superscript = mass number 6
12 C Left Subscript = atomic number 6
80 Br 35 Atomic Number = ?
20 Ne Mass Number = ?
27 Al Mass Number = ?
40 Ca 20 Atomic Number = ?
Isotope Atoms of the same element with a different # of neutrons
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?
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
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
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.
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.
Continuous Spectrum Spectrum produced by holding a prism in sunlight. Contains light at every wavelength.
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.