Atoms

Chemistry is about

• understanding the link between atomic structure, bonding, and properties.
• rxn -> structures and electrons change

Two Fundamental Building Blocks §

• matter
  • conservation of matter: matter cannot be created or destroyed
• energy
  • conservation of energy: energy cannot be created or detroyed
  • can be converted

Dalton’s Atomic Theory of Matter §

1. Matter consists of indivisible atom
2. All atoms of given element are identical in mass + properties
3. Atoms are indestructible and retain IDs during reaction
4. Atoms can combine to make compounds

Subparticles §

Electrons in Atoms §

• $e^{-}$
• $9.11\cdot 10^{-31}\text{ kg}$
• forms cloud around nucleus in orbitals

Nucleus §

• proton
  • $p^{+}$
  • $1.67\cdot 10^{-27}\text{ kg}$
• neutron
  • $n$
  • $1.67\cdot 10^{-27}\text{ kg}$
• mass number: sum of number of $p^{+}$ and number of $n$
  • ${}^{39}K$
  • defines isotope
• atomic number: number of $p^{+}$
  • ${}_{19}K$
  • defines element

Relation to mass §

• need to correlate atoms to mass
• use Avogadro’s Number
  • $N_A=6.022\cdot 10^{23}$
  • 1 mol = $N_A$ molecules, atoms, entities
• atomic mass units (amu)
  • unit of mass for atomic and molecular weights
  • $\frac{1}{12}$ of ${}^{12}C$ atom mass
  • $1.66\cdot 10^{-27}kg$
• molar mass (atomic mass/atomic weight/molecular weight)
  • $g/mol$
  • each atom has molar mass
  • $C{O}_2$
    • $12.011g/mol+2(15.999g/mol)=44.009g/mol$
    • To find molecules in $1g$,
    • $1g\cdot \frac{mol}{44.009g}\cdot \frac{6.022\cdot 10^{23}\text{molecules}}{mol}=1.37\cdot 10^{32}$ molecules