Chemistry 100: Group Exercise for Matter & Energy

Version A
Armando’s Copy
Chemistry 100: Summary of Chapters A & Q
These two chapters refine our knowledge of what atoms are and how they are made up. Unit A
deals with the discovery of subatomic particles and roughly how to organize the protons,
neutrons, and electrons. Unit Q shows us how the electrons are arranged in the atom – first with
the Bohr shells and then with the quantum mechanics model.
Compare this handout to the Key Terms and Concepts section at the end of the chapter.
We covered this information to reenforce the ideas of discovery, explanation of phenomena,
and the importance of being flexible about our favorite theories – they can be changed!
Important Topics
o Dalton’s Definitions (how many/which ones were shown to be wrong?)
o The 3 particles {protons, neutrons, electrons}, how heavy are they, what charge do they
o Isotopes (Dalton’s Rule #_____ out the window). Don’t do math on page A.9. Know A,
Z, how to find number of each particle in an isotope from nuclear symbol.
o Atomic Mass (amu) – 1amu ~ 1 hydrogen’s mass.
o Periodic Table: organize elements, # of atoms per row = Bohr Shells. Known the names
of columns (also called families or groups). Also know features of the table: metals/nonmetals, transition elements.
o Memorization: Memorize 1st 3 rows of periodic table: element name, symbol, number.
Look at Figure A.8 – we’ll probably know most of these by using them all quarter.
Armando’s Copy
Version A
This chapter introduces the system that shows how electrons are arranged in the atom. This
system explains just about everything in chemistry – that’s why we tackle such a tough block
of information.
Important Topics
o Light, Spectroscope: Don’t worry too much
about the deep details – but understand that the
thin colored lines from the Hydrogen lamp got
everything started.
o Bohr Model: Electrons orbit in shells with
different energies, 2 e- in 1st shell, 8 in 2nd &
3rd, 18 in 4th. Shell idea lasted into newer
Dark Violet
o Quantum Model:
Very weird but it works!
We now have 4 critera to identify electrons:
1. Principle Energy Level (n). Same as Bohr shell number.
2. Sublevel (s, p, d, or f). Shape of orbit.
3. Orbitals (x, y, z). Direction it points (up/down or left/right or front/back)
Pauli Exclusion Principle. Electrons are like children – they won’t share unless they
have to. They are also lazy.
Energy/Order of Orbitals. Use the triangle on pg Q.8, know the order. From
lowest energy to highest: n=1<2<3, s<p<d<f, Watch out: 3d<4s for some weird
Electron Configuration. Shorthand like a chemical formula – so we don’t have to
draw the 3D picture all the time. (e.g. 1s2 means 2 electrons in the s sublevel of the 1st
shell (n=1), 3p5 means 5 electrons in the p sublevel of the 3rd shell (n=3). For an
atom of Nitrogen: 1s22s22p3 – add up the superscripts, 2+2+3=7, Z=7 for nitrogen.
Be able to write the electronic configuration for any atom!
Valence Electrons. Electrons in the outer shell of an atom. We’ll use this a lot for
reactions and properties. Very simple to find: Locate the element on the periodic
table. Find its group number, that’s the number of valence electrons (Na: 1A, 1
valence electron. Cl: 7A, 7 valence electrons).
Chemical Families. We’ll talk about these – be able to locate them on the periodic
table. Be able to draw the atom’s Lewis Dot.
Lewis Dots. Another notation showing valence electrons for an atom. Put 1 dot for
each valence electron around the chemical symbol: Na, Mg:, :C: