Subdivisions of Matter Matter – Anything that occupies space and has inertia - Usually a mixture – Chemical with indefinite composition Molecule – Smallest subdivision of a substance that still has the properties of that substance - Substances – Have definite composition Atom – Smallest part of an element that still has the physical properties of that element - Elements – Substances that can’t be broken down into simpler substances by ordinary means - Compounds – 2 or more elements in definite proportions

Elements combine to form compounds

Theory of Atomic Structure Neils Bohr (1913) – Theorized the concept of the atom as a solar system Consists of 3 Sub-Atomic Particles: - Protons – Positive particles in nucleus 1,828 X heavier than electrons - Neutrons – Neutral particles in nucleus - Electrons – Negative particles Orbit the nucleus Electrical in nature

The Atom Consist of shells K = 2 electrons L = 8 electrons M = 18 electrons N = 32 electrons 2(N) 2 – Formula showing # of electrons in an atom where “N” is the number of the electron shell Octet Rule – An atom is chemically stable when there are 8 outer shell electrons Binding energy – Greater for inner shells Electron Energy – Greater for outer shells

Sub-Atomic Structure Atomic Number – Number of protons in nucleus - Determine the type of element - Equals the number of protons in stable atoms - Designated by symbol Z Atomic Mass – Number of protons and neutrons in nucleus Isotopes – Atoms with the same number of protons (equal to the original element), but different number of neutrons (different atomic mass) Nuclide – A particular type of atom defined by its number of protons and neutrons

Isotopes of the Element Hydrogen Each has the same number of protons and are therefore hydrogen. However, each has a different number of neutrons, which makes them isotopes

Chemical Behaviors The Periodic Table Columns have similar chemical properties (Same number of outer shell electrons) Rows have different chemical properties (Same number of shells, but different number of outer shell electrons) # Below each element indicates atomic No. # above each element indicates atomic wt.

What determines the chemical properties of an element? Valence – How one element combines with another Determined by number of outer shell electrons All elements gravitate towards stability (8 electrons in outer shell – the Octet Rule) Elements with 1 outer shell electron have a +1 valence (one to give) - Example Na Elements with 7 outer shell electrons have a -1 valence (will accept an electron) - Example Cl These are known as ions – Atoms with a plus or minus charge Opposite charges attract to form ionic bonds Na + Cl = NaCl

Covalent Bonding Sharing of outer shell electrons to form a chemical bond

Ionization The process of adding or removing electrons from an atom. Loss of an electron causes the atom to become positively charged Adding an electron causes the atom to become negatively charged

Methods of Ionization X-ray Bombardment Electron Bombardment Spontaneous Breakdown Light Bombardment Chemical Ionization Thermionic Emission