C#3 2022

C#3 2022

1. atom

   • strong electrostatic forces of attraction between protons in nucleus and electrons
   • mass of atom concentrated in nucleus --> mass of atom almost entirely due to nucleus
   • nucleus contains protons and neutrons
   • electrons revolve around nucleus at great speed. arranged in electron shells. each shell associated with specific energy level. (nearer to nucleus --> lower energy level)
   • atom electrically neutral so p=e
   • electrons in outermost shell called valence electrons - determine chemical properties of element
   • proton no unique to an element

2. periodic table

   • atomic / proton no. --> no. of protons in nucleus of atom
   • mass / nucleon no. --> total no. of protons and neutrons n atom
   • nuclide notation
   • periodic table format - atomic no. above. mass no. below
   • group no = no of valence electrons
   • period no = no of electron shells
   • grp I to III --> metals. grp IV to 0 --> non-metals
   • grp 0 - noble / rare / inert gases - full valence shell. do not want to bond with other atoms (monatic) - unreactive

3. drawing

   • atomic structure - show nucleus with p & n
   • electronic structure - only show element symbol. no nucleus

4. isotopes

   • atoms of same element with same no of protons but diff no of neutrons
   • relative atomic mass; average of atomic masses of isotopes
   • have diff mass
   • similar chemical properties bc isotopes have same no of valence electrons
   • diff physical properties bc diff no of neutrons

5. ions

   • charged particle
   • formed when atom gains/ loses electrons
     • metals form positively charged ions - cations by losing electrons (have more protons than electrons)
     • non-metals form negatively charged ions - anions by gaining electrons (have more electrons than protons)
       • anions are named '__ide' ions (e.g. oxide, flouride)

6. molecules

   • formed when atoms come together to share electrons (covalent bonding)

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