How Atoms Differ Objectives Covered in this Presentation: 7. Locate the three fundamental particles in the atom; indicate the relative mass and charge of these particles. 8. Indicate what the atomic number and mass number of an atom represent. 9. Calculate the mass number when given the number of protons and neutrons. 10. Indicate which isotope is used as the standard for atomic mass. 11. Write the nuclear symbol for an atom. 12. Determine the number of protons, neutrons, and electrons when given the atomic number and mass number. 13. Calculate average atomic mass from relative abundance. 14. Define isotope and identify which nuclides are isotopes of the same element when given the atomic number and mass number of these nuclides.

Atomic structure Protons: positive particles in nucleus Neutrons: particle with no charge in the nucleus Electron: particle with negative charge orbiting the nucleus

Subatomic particles Quarks: make up protons and neutrons Six types: up, down, strange, charm, truth (top) and beauty (bottom) (I am not making up those names, nuclear physicists can be weird.)

Subatomic Particles (Cont) Other subatomic particles include leptons, neutrino, tau, muon etc.

Atomic Symbols SI symbols used internationally. Based on Greek, Latin, a person’s name, or location discovered. Examples: Iron : Fe Silver : Ag

Atomic Symbols 1 st letter capitalized 2 nd and 3 rd letter lower case MUST be printed in traditional letters NO cursive Aluminum: Al not Al Cobalt: Co not CO or co

Atomic Number Equal to the number of protons The number of protons for an element never changes

Atomic Number In a stable atom, the number of protons = electrons The positive and negative charges are equal and the overall charge is neutral

Nuclear Charge If electrons are gained, the number of electrons is greater than the number of protons and the charge is __________

Electric Charge If electrons are lost, the number of electrons is less than the number of protons and the charge is __________

Atomic Mass May be noted as mass weight, or atomic weight Equals: protons + neutrons

Atomic Mass Each proton and each neutron have an atomic mass of 1 amu. (Atomic mass units). Electrons are so tiny ( amu) that their mass is negligible.

Atomic Mass is an Average Remember: the number of protons for any element does not change The number of neutrons does vary.

Example: All carbon atoms have 6 protons. Most carbon atoms has 6 neutrons, but very few have 8. 6P + 6N = 12 amu 6P + 8N = 14 amu

If you have 9 carbon atoms with 12 amu and 1 carbon atom with 14 amu, what is the average amu?

If you have 9 carbon atoms with 12 amu and 1 with 14 amu, what is the average amu? 9 atoms X 12 amu = atom X 14 amu = = /10 =12.2 amu

Isotopes: atoms of the same element with different numbers of neutrons and slightly different amu. The greater the number of protons for an element, the greater the number of isotopes.

Periodic Table History: 1869 Mendeleev created 1 st Periodic Table. He arranged it by atomic mass and successfully predicted unknown elements.

Modern Periodic Table: Arranged by atomic number List element name Element symbol Atomic number Atomic mass

Periods: (rows) all elements in the row have the same number of energy levels Families: (column) have the same number of valence electrons and oxidation state.

Valence electrons: number of electrons in the outer most energy level Oxidation state: number of electrons needed to be gained or lost to have 8.

Using the periodic table Protons = ?

Using the periodic table Protons = atomic number Electrons = ?

Electrons = number of protons Neutron = ?

Neutrons = atomic mass – atomic number