Grouped by Chemical/Physical Properties

Periodic Table

Grouped by chemical/physical properties

Arranged by atomic number

· Elements to the left of the zigzag line of the periodic table are classified as metals. Those to the right of the zigzag line are classified as nonmetals and those that scatter either side of the zigzag line are metalloids.

o Metals make up the majority of the periodic table.

· Same period ↔ = same # of electron shells

· Same family ↕ = similar physical and chemical properties.

o A family or group have same # of electrons in outer shell (valence electrons)

· In first electron shell of all elements, the maximum # of electrons is 2

· If an atom has 8 valence electrons, it is a happy atom.. (Noble Gas)

Atomic number = number of protons

# of protons = number of electrons

Mass = protons + neutrons OR mass – atomic number = neutrons

Atoms – smallest amount of an element

· Atoms of different elements have different masses (mass found in the nucleus)

· All atoms of a particular element are exactly the same--same structure and same amount of matter.

· The atoms of one element are different from the atoms of another element--same basic structure, BUT different amounts of matter.

· When atoms of different elements chemically combine, they form a compound.

· If you break an atom into protons, neutrons and electrons, those pieces no longer represent the element. Only when those subatomic particles are combined the proper way, do you have atoms of a specific element.

· All atoms in the universe (no matter from what element) have the same structure.

· A nucleus made of protons and neutrons

· Electron cloud containing electrons which orbit the nucleus

· Most of the mass in an atom is in its nucleus.

· Electrons have very little mass.

· All atoms in the universe (no matter from what element) are electrically neutral.

· # of protons = # electrons

· Protons have a positive charge.

· Electrons have a negative charge.

· Neutrons have no charge.

So, the # of positives in an atom equals the # of negatives, which means no charge for the atom.

· The atoms of each element have a certain number of protons in the nucleus.

· All atoms of a particular element are exactly the same, with the same number of protons in the nucleus.

· The atoms of one element are different from the atoms of another element because each element has its own unique number of protons in the nucleus.

· The atomic number of an element tells you how many protons are in the nucleus of its atoms.

Density

· The amount of mass per unit volume of a given object.

o D= m/v

· If the density of the object and either mass or volume is known

o M = d ● v

o V = m/d

· Densest liquids settle to the bottom of a container least dense will float

· Density of water is one. If an object is more dense it will sink, if it is less dense it will float.

Properties of Matter

o Made of small particles called atoms and molecules that are in constant motion.

o Has mass and volume (takes up space)

o Exhibits inertia

o Can’t occupy the same space as other matter

Law of Conservation of Mass

· The Law of Conservation of Mass states: mass cannot be created nor destroyed in a chemical reaction.

o The mass of the products in a chemical reaction must equal the mass of the reactants.

§ Reactants are before the arrow and products are after the arrow

o A change of state is a PHYSICAL change. The substance itself stays the same.

o i.e. – Melting chocolate is still chocolate

(Remember: in a chemical change, you end up with an entirely NEW substance!)

· Physical changes can be observed without the substance changing to an entirely new substance.

o Phase changes are physical changes. Even though the state of matter is different, the substance and its molecules and atoms are the same.

· Chemical changes can be observed when a new substance, different from the original substances, is produced.

o Chemical changes often produce light and energy.

o A chemical change can cause energy to be given away or to be absorbed.

· Endothermic Reaction - a chemical reaction (change), a substance absorbs energy

· Exothermic Reaction - a chemical reaction (change), a substance releases energy

· On the pH scale 7 is neutral, below 7 are acids and above 7 are bases.