Molecule Intro Notes

Atom: smallest unit of matter that constitutes a chemical element

Element: substance that cannot be broken down into smaller smaller substances

Molecule: group of atoms bonded together

• Element Molecule: multiple atoms of the same element bonded together
• Compound Molecule: atoms of different elements bonded together

Mixture: substance made by combining other substances

• Homogenous Mixture: mixture with same proportions of components throughout (uniform)
• Heterogenous Mixture: mixture that is not uniform throughtout

https://www.diffen.com/difference/Compound_vs_Mixture (Links to an external site.)

Types of bonds

Ionic Bond: ions bonded due to the transfer of electrons

• One atom gains electrons, the other loses electrons
• One becomes negatively charged, the other becomes positively charged
• Opposites attract, so they stick together

https://www.quora.com/What-are-ionic-covalent-and-metallic-bonds (Links to an external site.)

Covalent Bonds: atoms bonded by sharing electrons

• shared electrons create a new orbit around both atoms

https://www.quora.com/What-are-ionic-covalent-and-metallic-bonds (Links to an external site.)

Writing molecular formulas

1. Determine the number of each type of atom in a compound, based on the prefix:
   • "mono" = 1
   • "di" = 2
   • "tri" =3
   • "tetra" = 4
     • Example: Carbon dioxide--"di" means it has two oxygen atoms
     • No prefix before "carbon" means there is 1 carbon atom
2. Write the symbol for the first element
   • C for Carbon
3. Write how many atoms of that element as a subscript
   • subscript= number written slightly below the normal line of text
   • If there is only 1 atom of an element, do not write a subscript
     • Example: Only one C in Carbon dioxide, so just write C
     • Two Hydrogen in Dihydrogen monoxide: write "H₂"
       
4. Repeat for the next element in the compound
   • Example: Carbon dioxide
     • "di" means 2 oxygen
     • write as O₂
     • combined with the first element: CO₂
   • Example: Dihydrogen monoxide
     • "mono" means 1 (which we never write in a formula), so 1 oxygen
     • H₂O