Number of Protons Atomic Number
Number of Protons + Neutrons Mass Number
Left Superscript = mass number 6
Left Subscript = atomic number 6
35 80Br 35 Atomic Number = ?
20 20Ne 10 Mass Number = ?
27 27Al 13 Mass Number = ?
20 40Ca 20 Atomic Number = ?
# of electrons in a neutral atom? Neutral atoms have the same number of electrons and protons. # of electrons in a neutral atom?
Atoms of the same element with a different # of neutrons Isotope
Characteristics of Proton Charge = +1, mass = 1 amu, location = inside nucleus Characteristics of Proton
Characteristics of Neutron Charge = 0, mass = 1 amu, location = inside nucleus Characteristics of Neutron
Characteristics of Electron Charge = -1, mass = 1/1836 amu or 0.0005 amu, location = outside nucleus Characteristics of Electron
An atom that has gained or lost electrons & so carries charge Ion
An atom that has LOST electrons Positive Ion
An atom that has GAINED electrons Negative Ion
# protons - # electrons Charge
Protons & Neutrons Nucleons
Smallest bit of an element that retains the properties of the element. atom
Mass number – atomic number # of neutrons
8 neutrons 6 protons 6 electrons # of neutrons = ? # of protons = ? # of electrons = ?
5 neutrons 4 protons 4 electrons 9Be 4 # of neutrons = ? # of protons = ? # of electrons = ?
22 neutrons 18 protons 18 electrons 40Ar 18 # of neutrons = ? # of protons = ? # of electrons = ?
8 neutrons 7 protons 7 electrons # of neutrons = ? # of protons = ? # of electrons = ?
Right superscript = charge 24Mg 2+ 12
8 neutrons 7 protons 10 electrons (gained 3) -3 7 # of neutrons = ? # of protons = ? # of electrons = ?
10 neutrons 9 protons 10 electrons (gained 1) 19F -1 9 # of neutrons = ? # of protons = ? # of electrons = ?
8 neutrons 8 protons 10 electrons (gained 2) -2 8 # of neutrons = ? # of protons = ? # of electrons = ?
12 neutrons 11 protons 10 electrons (lost 1) 23Na +1 11 # of neutrons = ? # of protons = ? # of electrons = ?
12 neutrons 12 protons 10 electrons (lost 2) 24Mg +2 12 # of neutrons = ? # of protons = ? # of electrons = ?
14 neutrons 13 protons 10 electrons (lost 3) 27Al +3 13 # of neutrons = ? # of protons = ? # of electrons = ?
Charge on the nucleus only. Does not include the electrons. Always positive. Equals the number of protons. Nuclear Charge
Positive ion Cation
Negative ion Anion
Billiard Ball Model Dalton’s Model
Atoms are hard, round, indivisible. They are solid & uniform throughout. Dalton’s model
Plum Pudding Model Thomson’s Model + - - + - + + - + -
Thomson’s model Atoms are divisible. They are solid but NOT uniform throughout. They contain + and - charges. The – charges are little particles. Thomson’s model
Nuclear Model Rutherford’s Model - + - -
Atoms are divisible. Atoms are NOT solid. Atoms are NOT uniform. They contain + and - charges. Most of the mass and all of the + charge is concentrated in the nucleus of the atom. Most of the volume is empty space. Rutherford’s model
Rutherford’s Experiment Shot α particles at gold foil. Most went through, so most of the atom is empty space. Some deflected back by small dense positive nucleus. Rutherford’s Experiment
Planetary Model Bohr’s Model
The mass of the entire atom: includes protons, neutrons, electrons The mass of the entire atom: includes protons, neutrons, electrons. Expressed relative to the mass of a C-12 atom. atomic mass
atomic mass unit 1 atomic mass unit 1/12 the mass of a C-12 atom. or The C-12 atom has a mass of 12.000 . . . atomic mass units. atomic mass unit
The weighted average of the masses of the naturally occurring isotopes of an element. Average atomic mass
Average atomic mass Convert % abundance to decimal format. Multiply abundance factor by appropriate mass. Sum Average atomic mass
Quick check on average atomic mass calculation. Final answer must be between the highest & lowest masses. Final answer will be closest to mass of most abundant isotope. Quick check on average atomic mass calculation.
75% = .75 and 25% = .25 (.75) X 35 = 26.25 (.25) X 37 = 9.25 26.25 + 9.25 = 35.5 = avg. atomic mass of Cl Ans is between 35 & 37, but closer to 35. Calculate the average atomic mass of Cl. 75% is Cl-35 and 25% is Cl-37.