Levels of Chemistry
Macroscale Level: Human Level, Observations
Symbolic Level: Representation Level, Symbols, Formuls, Equations
Nanoscale Level: Particle Level, Models
Physical Properties of Matter
Matter: anything that is occupying space or has a mass.
Solid: rigid, fixed volume and shape.
Liquid: definite volume but assumes the shape of container.
Gas: no fixed volume or shape, assumes the shape of its container.
Liquid and Gas are fluid**
6. Melting point
7. Boiling point
10.Shape of solid crystals
**Dependence of the properties on the amount of the sample.
Extensive properties: depends on amount of sample.
Intensive properties: independent of the amount of the sample.
4. Heat capacity
3. Melting point
4. Boiling point
5. Hardness 6. Density
Percent Composition of Mixtures
Mixtures have variable composition
Homogeneous mixture: looks completely uniform and consists of two or more
substances in the same phase. (Solutions)
Heterogeneous mixture: is clearly not uniform when seen without magnification.
%A= (amount of A/total amounts of A and B)x100%
Atoms, Molecules, Elements and Compounds
Heterogeneous Homogeneous Compounds Elements
Compound: a pure substance with a constant composition that can be broken down
into elements by chemical processes.
Element: a pure substance that cannot be decomposed into simpler substances by
Introduced the concept f the smallest possible particle of matter.
Atoms >> atomos: cannot be divided. Dalton’s Atomic Theory
1. Each element is formed of extremely small particles called atoms.
2. Atoms of a given element are identical; atoms of different elements differ in
some fundamental ways.
3. Chemical compounds form when atoms combine with one another. A given
compound always has the same relative number and types of atoms.
4. Chemical reactions involve reorganization of the atoms. Atoms change the
way they are bound together. During the process, atoms are NOT created or
Atom: the smallest particle of an element that can exist. They differ as a function of
their mass and other properties.
Element: a substance composed of only one kind of atom.
Elements can exist as single atoms or molecules.
Molecules are a definite and distinct group of atoms bound together.
Allotropes: different forms of the same element that exist in the same physical state
at the same temperature and pressure. (Ex. O2, O3. Oxygen and Ozone.)
Compound: a substance that consists of two or more different elements with their
atoms in a definite, characteristic ratio. (Ex. H2O, CO2, CO. Water, Carbon Dioxide,
Language of Chemistry: Intro to Nomenclature
Types of Elements:
1. Non-metals: do not conduct electricity, are not malleable or ductile.
2. Semi-Metals: show mixtures of metallic and non metallic properties.
3. Metals: conduct electricity, have metallic luster and are malleable and ductile.
Language of Chemistry: The Periodic Table
Rutherford’s Model of Atom
Atom is composed of mainly vacant space.
All the positive charge and most of the mass is in the nucleus.
Neutrons are also present in the nucleus.
Electrons are dispersed as layers around the nucleus.
The atomic number (Z): number of protons (equal to electrons in a neutral atom.)
Atomic Mass (A): sum of number of protons and neutrons in the nucleus.
(A = Z + N)
Group 1: Alkali Metals Group 2: Alkali Earth Metals
Group 17: Halogens
Group 18: Noble Gases
Group 3-12: Transition Metals
Lanthanides (rare earth metals)
Actinides (trans-uranium series)
Valence Shell Electrons
Electrons are present in layer around the nucleus.
Electrons in the outermost shell are called valence shell electrons.
These electrons are very important as they interact with other valence shell
electrons of other atoms and bonding.
For main group elements the number of valence electrons corresponds to
their position in their periodic table.
Language of Chemistry: Oxidation States
For an atom, electrons can be lost or gained during chemical reactions.
The state becomes more positive.
The state becomes more negative.
Oxidation number is the number of electrons or gained during a chemical change.
Rules for Oxidation State:
1. Of an atom in a pure element = 0
2. Monotomic ion = charge
3. Oxygen = -2
4. H with non-metal = 1
5. H with metal = -1
6. Fluorine in compounds = -1
7. Sum of O.S. is 0 in compounds
8. Sum of O.S equals charge of ions
Elements with Fixed Oxidation State
1. Group 1: Always +1
2. Group 2: Always +2
3. Fluorine in fluorides: Always -1
4. Oxygen in oxides: Always -2
5. Aluminum & Scandium: Always +3
6. Zinc and Cadmium: Always +2 7. Silver: Always +1
Language of Chemistry: Lewis Symbols and Lewis Structures
Lewis Symbol: chemical symbol of an element surrounded by dots representing its
For ionic compounds, dots are removed from the Lewis symbol of the metal atom
and transferred to the Lewis symbol of the nonmetal atom to complete its valence
shell upon balancing the charges.
Lewis structures: show how valence electrons are arranged among atoms in a
Simplified Octet Rule: when compounds form, certain atoms gain or lose electrons
until their respective valence shells possess eight electrons.
In covalent bonds atoms share pairs of electrons until they reach a noble gas