Atomic Mass & Electrons Notes

Atomic Mass Mass of a neutron or proton is approx. at one atomic mass unit or Dalton (Da) masses of electrons that are tiny Ignored Atomic number is fixed if we change the number we change the actual nature of the atom. However we can have a single atomic number and Change the mass of that atom by adding or Subtracting neutrons we create isotopes of it Ex ¹²C CCC + Neutron + Neutron 6 CCC ¹³C ¹⁴C The most abundant Carbon isotope Home number stays the same Electrons! -Travel around atomic nuclei in orbitals -Orbitals are grouped into layers or Shells based on how far the electrons in that shal travel from the nucleus   Nucleus 1St Shell 2nd Shell 3rd Shell max 2e man Be- Max Be- Prolen ↓ will be Constantly moving The inner most shell is filled first Once that shell is filled with a pair of electrons, the next shell will fill with 2 singles then subsequent electrons form pairs The outermost Valence electrons determines the number of bonds an atom Can make Valence electrons: Electrons in the outermost shell unpaired valence electrons determine the # of bonds the atom will make.   12C 35Cl 40Ar 18 6 17 Carbon: 4 unpaired Electrons Chlorine: 1 Argon: 0 unpaired electrons 6. A Non reactive element. Paired electron. atomic number Completely filled Valenced Shells •Non reactive (Stable) eg He, Ne, Ar electron shell 1 Hydrogen element IV 2 Helium Closest to filling the shells 6 Carbon Host reactive eg. CI, FI, O 7 Nitrogen. 8 Oxygen 10 Neon 11 Sodium Atoms with the same # of valene 12 Magnesium electrons 15 Phosphorus 16 Sulfur •Have Simiter behaviour 17 Chlorine •Forms basis for periodic table 18 Argon Elements abundant in organisms have at 19 Potassium least Crie UNPAIRED electron. 20 Calcium