What is a compound?
- Compounds are pure substances.
- They are made up of chemical combinations of the elements.
What are molecular compounds?
- They are made of non-metals.
- They stay together by sharing electrons in their valence shells. Held together by covalent bonds (always pairs of electrons)
Ex: H2O, CH4, etc.
What is a “stable octet”?
- It means an atom wants to have 8 electrons in its valence shell.
- The only atom that will be stable with 2 electrons in its valence shell is hydrogen.
What are diatomic molecules?
Diatomic molecules are molecules that contain only two atoms bonded to one another.
Seven diatomic elements: HOFBrINCl the clown.
What are the hydrocarbons?
They are compounds that only have carbon and hydrogen atoms.
Ex.
- CH4: Methane
- C2H4: Ethene
- C3H8: Propane
The diagrams for Molecular Compounds (3):
- Bohr-Rutherford (Solar System)
- Model Diagram (One spring = one covalent bond)
- Stick Diagram (One bond = one hyphen. Ex: Cl2 = Cl–Cl)
Name 5 compounds:
- H2O: Water
- CH4: Methane
- NH3: Ammonia
- CO2: Carbon Dioxide
- H2O2: Hydrogen Peroxide
What are ions?
A particle with a charge. They can be positive or negative.
- Cation: Positive (+)
- Anion: Negative (-)
- They have full valence shells.
Metal Elements:
- Groups #1, 2, 13.
- Have < 4 Valence Electrons.
- They give these Valence Electrons away.
- They are all positively charged.
Ex: Be2+
Non-Metal Elements:
- Groups # 15, 16, 17
- Have > 4 Valence Electrons.
- They pick up enough electrons to fill their valence shells.
- They now have a negative charge.
Ex: F1-
Where do you put the charge of an ion?
It is written as an exponent. (Negative/Positive)
What are Ionic Compounds?
- Metal + Non-Metal
- Neutral (Total positive charge equals total negative charge)
+ create another ion if valence electrons cannot be properly distributed.
What is the difference between Molecular and Ionic Compounds?
Molecular:
- Non-Metal + Non-Metal
- Connected by Covalent bonds
- Poor conductors of electricity
- Solid, Liquid, or Gas
- Made of atoms
Ionic:
- Non-metal + Metal
- Connected by Ionic Bonds
- Conducts electricity
- Solid
- Made of ions
What is a covalent bond?
A covalent bond is a bond formed between two non-metal atoms sharing electrons.
The diagrams for Ionic Compounds:
- Bohr-Rutherford (giving/taking away electrons)
- Electron Dot Diagram: In square brackets, charges outside, negative ions have 8 dots surrounding the element.
How do atoms become ions?
Atoms become Ions by either giving up or taking electrons.
Electrical Law:
Two ions are attracted to each other because of the electrical law: opposite charges attract.
Why don’t group #18 elements make ionic compounds?
Group #18 elements do not make ionic compounds because their valence shells are full. (He= 2, everything else = 8)
