Atoms, compounds, and ions

Introduction to the atom

• 1 Mole=6.02*10²³ = Avogadro's number
• 1 Mole(6.02*10²³) of ¹²C atoms in 12g of C
• mole's role: switching between amu and g
• 1g=1mole of amu=6.02*10²³amu
• 1more of ²⁷AI=27grams
• 1mole of ⁵⁶Fe=56grams
• A(mass number)=Z(atomic number=proton number)+N(neutron number)
• ¹⁸Fe^- consists of: 9 proton, 9 neutron, 10 electron

ions and compounds

• in covalent bonds, atoms share electrons
• a group of atoms joined by covalent bonds is a molecule
• there is NO such thing as a molecule of an ionic bond
• in ion bonds, electrons are fully transferred between two atoms, so that ions are formed
• ionic bond: two oppositely charged ions attract each other
• 
• representing molecules: chemical formula, structural formula
• *the group 3A elements link

names and formulas of ionic compounds

• cation: ion with net positive charge
• anion: ion with net negative charge
• predicting charges on monatomic cations and anions
• groups 1,2,13,14: usually give away valence electrons to become ions(C is sometimes an exception)
• groups 15,16,17: usually negative charge, because is more likely to gain electrons not lose
• most of the transition metals(d-block)are polyvalent
• naming of transition metal cation: chromium(II)chloride=Cr²⁺
• naming anions: add suffix '-ide'
• formulas and naming of basic ionic compounds: 

1. always name the cation(+)before the anion(-)
2. when naming the cation, don't include the word ion or charge unless it's a polyvalent ion
3. any ionic compounds have a net charge of zero(they cancle each other)

• polyatomic ions: the ion that contains more than one atom
• polyatomic ion is formed when a neutral molecule(covalent bond) gain or lose electrons
• the chemical formula of calcium hydroxide is: Ca(OH)2 not CaOH2

Isotopes and mass spectrometry 

• isotope: same # of proton, electron but different # of neutron
• atomic weights: weighted average calculated by summing up each isotope's atomic mass
• mass number=number of netrons+number of protons(atomic number)
• 1u(amu)=1/12 of the mass of single neutral atom of carbon-12 *12 is the mass #
• mass of a neutron=1amu
• mass of a proton=1amu
• mass of an electron=considered to be zero amu
• atomic mass=how many protons and neutrons*1amu(not exact, but close)