Material Historicos De Los Alemanes Futuristicos

Chemistry
Physical and Chemical Changes
• Chemical Changes: These occur when a substance combines with another to form a new substance.
Examples include:
* Rotting fruit
* Mixing chemicals
* Tarnishing silver.

• Physical changes: These are changes that affect the form of an object, but ultimately doesn’t have any effect on its chemical composition.
Examples include:
*Tearing a piece of tin foil.
* Crumpling a piece of paper.

Differences between the two:
1. A physical change is reversible, a chemical change is not.
2. A physical change is a change in which no new substance is formed; a chemical change results in the formation of one or more new substances.

Mixture: Contains more than one substance. They are just mixed together and notchemically combined.
 Example: Sand and water.
Elements: This is a substance with only one type of atom. Example: Oxygen or Helium
Compounds: This is a two or more elements chemically combined together.
Example: Carbon Dioxide or Water.
• Atoms are the smallest particles.
• Each atom consists of a nucleus and a cloud of particles called electrons that whizz around the nucleus.
• An element is asubstance that contains only one kind of atom.
The groups of elements that have similar properties are put in a numbered column.

The rows are called periods.
The zigzag line separates metals from non-metals, with the non-metals on the right.
So most elements are metals.
• A compound contains atoms of different elements joined together where the atoms are chemically combined. For examplecarbon dioxide is a compound of carbon and oxygen (1 carbon and 2 oxygen molecules).
• Compounds are “chemically” joined together, mixtures are not so mixtures can often be easily separated from its joining parts.
Atomic Structure and the Periodic Table
An atom consists of what we call, Subatomic Particles, the things that make up the atoms.

• Green circle: Neutron.
• Red circle: Proton.• Yellow circle: Electron
• Neutron + Proton: Nucleus.
Orbiting the nucleus are the electrons called “Electron Orbitals”

• Electrons are arranged in shells.
• Each group is equivalent to one energy level and when you reach the end of the period of the group, you start off at a new group.
* 1st energy level holds up to 2 electrons
* 2nd energy level holds up to 8 electrons
*3rd energy level holds up to 8 electrons.
• If an atom has its 3rd energy level holding 8 electrons, 2 more electrons will push it to the 4th energy.
• The atoms at the end of the periodic table have a full electron shell, no more additional electrons may be added on and it has no valence electrons.
• We call these Noble Gases.
Particle in the Atom | Mass | Charge |
Protons | 1 | +1 |Neutrons | 1 | 0 |
Electrons | Almost 0 | -1 |
Proton Number: The number of protons found in the nucleus. This is the same as the Atomic Number.
Nucleon Number: This is the number of protons and neutrons located in the nucleus of the atom.
• Each time you go across a period, lets say Helium, the atom has one more proton that the element on the left.
• Example: Hydrogen has one proton, andHelium has two. Lithium is now down a group so it has 3 protons.
• Moving along the period, you have Beryllium, Boron, Carbon, Nitrogen, Oxygen and so on…
Isotopes: are atoms of the same element, with the same number of protons but different number of neutrons.
Ions and Ionic Bonds
• An atom is pretty stable.
• They have an equal number of electrons and protons.
• Atoms often have thepotential to become unstable. The truth is, most atoms don’t like to have outer electrons.
• Noble gases in group 8, they don’t have any outer electrons.
• Elements in group 1-7 all want to become like a noble gases in terms of electron configuration.
• If an atom loses or gains an electron, we call it an ion.
Sodium has an electron configuration of 2,8,1, so it has one outer electron.
It...