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UNIT 2 REview. Science 10. Bohr Diagrams. Electrons appear in shells in a very predictable manner. There is a maximum of 2 electrons in the first shell, 8 in the 2nd shell, and 8 in the 3rd shell. The period # = # of shells in the atom. Except for the transition elements,
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UNIT 2 REview Science 10
Bohr Diagrams • Electrons appear in shells in a very predictable manner. • There is a maximum of 2 electrons in the first shell, 8 in the 2nd shell, and 8 in the 3rd shell. • The period # = # of shells in the atom. • Except for the transition elements, the last digit of the group # = # of electrons in the valence shell
Periodic Trends • Look at Elements on the periodic table and be able to determine • Protons • Electrons • Mass number • Atomic number • Net charge (if possible) Of the stable atoms and the isotopes.
Naming/Writing formulas of chemical compounds • Name and write formulas for Ionic and covalent compounds • magnesium and nitrogen • Magnesium nitride
K3N • K3N • A. Step 1 Identify the ions K=potassium N=Nitrogen Step 2 check the charges K=+1 N=-3 Step 3 Determine the ratio 3 potassium ions for every nitrogen ion
K3N • Balance the charge therefore means that potassium must have a charge of +1 if it takes 3 potssium ions to balance a charge of -3 • Or you could cross the subscripts back over to superscripts • K3 N1 • K+1N-3 • Potassium nitride
potassium bromide • Step 1: determine the charges and symbols Potassium=___ Charge: +1 Bromide=____ Charge: -1
Step 2 write superscripts with the symbols and cross over the subscripts • K+1 Br-1 • K1 Br1 • Answer is: KBr When writing names for multivalent formulas make, cross the subscripts back to superscripts then verify that the charge does exist on the periodic table.
Balancing equations • Go from word equations to skeleton equation • Balance equation using the plan strategy • 1.leave anything that appears in more than one species (or compound) to end • Leave elemental forms • Balance groups (polyatomic ions) • Let the coefficients lead you • Classify as S, D, SR, DR, C, N
Example • See overhead
Know how to use the PH charts • Need to know how to determine whether a chemical is an acid or a base according to what colour the indicator has turned
Radioactive Decay • Alpha decay • Beta decay • Gamma decay • See overhead for example
Nuclear Fission and fusion • Fission • Splitting of more massive nucleus into two less massive nuclei, subatomic particles and energy • Induced or forced • Rules • 1. mass of numbers on each side of equation stays the same • 2. Sum of the charges on each side of equation stays the same
Fission • See overhead for example
Fusion • Two low mass nuclei join to form a more massive nuclei • Occurs in the sun • Study Table 7.11 page 321
Fusion • Example see overhead