1. Modern periodic table is based on atomic numbers.
2. Groups are up and down
3. Periods are left to right.
4. Period 1 is the only period that is all gases.
5. The period number indicates the energy level of the valence electron.
6. All elements in a group have similar characteristics.
7. All elements in a group have the same number of valence electrons.
8. Names and symbols are found on table S.
9. Atomic masses are found in the upper left corner of each element’s box. Round them to the nearest tenth when asked.
10. Atomic numbers are located in the bottom left corner right above the electron configuration. Each element has a unique atomic number.
11. Be able to read electron configurations. Example: 2 – 4 is the electron configuration of carbon. There are two electrons in the first energy level and 4 valence electrons in the second energy level.
12. The first nrg level can hold a maximum of 2 electrons. Second can hold 8. Third can hold 18. Fourth can hold 32. formula 2n2
13. Metals are found to the left of the staircase.
14. Nonmetals are to the right of the staircase.
15. Metalloids are B, Si, Ge, As, Sb, Te, and Po.
16. Properties of metals:
a. lose electrons to form positive ions
b. malleable and ductile
c. have metallic luster
d. Hg (mercury) only liquid metal
e. Metals conduct electricity in both the liquid and solid phases because metallic bonds have free moving electrons.
f. Low ionization energies and low electronegativities
g. The more reactive the metal the lower the ionization nrg.
17. Transition metals form colored compounds and colored solns. Cu is blue. They lose electrons from two different energy levels.
18. Metalloids act as metals or nonmetals
19. Properties of non metals:
a. Most are gases at room temp.
b. Bromine is a liquid non metal
c. Non metallic solids are brittle
d. Poor conductors of electricity
e. High ionization energies and electronegativities.
f. Diatomic elements. Br2 I2 N2Cl2H2O2F2. Exist as two atoms bonded together in nature. Always O2 never just O
20. Noble gases are unreactive due to their 8 valence electrons. Xe and Kr may react with F.
21. Noble gases are monatomic gases. Single atom molecules.
22. Iodine is a solid.
23. Allotropes are two forms of the same element. Ozone (O3 ) and O2 are allotropes
24. Ionization energy is the amount of energy to remove 1 valence electron.
25. Electronegativity is the attraction an atom has for an electron in a chemical bond.
26. Atomic radius is the HALF the distance between nuclei of bonded atoms.
27. Periodic Trends: You must know trends and explanations!
A. Radius increases down a group because the number of energy levels increases as period number increases.
B. Radius decreases from left to right across a period because the nuclear charge increases and the number of energy levels remains the same.
C. Ionization energy decreases down a group because the valence electrons are further away from the nucleus.
D. Ionization energy increases across a period because the nuclear charge increases and the number of energy levels remains the same.
E. Electronegativity decreases down a group because the valence electrons are further away from the nucleus.
F. Electronegativity increases across a period because the nuclear charge increases and the number of energy levels remains the same.
G. Reactivity of metals increases down a group because ionization energy decreases.
H. Reactivity of non metals decreases down a group because electronegativity decreases.
I. Lower left of periodic table are the most reactive metals.
J. Flourine is the most reactive nonmetal.
28. Alkali metals are group 1. Most reactive. Never found uncombined in nature. Isolate them from compounds using electrolysis. They have 1 valence electron and form + 1 ions.
29. Alkaline earth metals are group 2. Second most reactive metals. They have 2 valence electrons and form + 2 ions.
30. Halogens are group 17. Halides are the ion form of group 17 elements. Most reactive nonmetals. Not found uncombined in nature.
31. Hydrogen is not an alkali metal. It’s a gas.
32. alkali + halogen = MX always 1:1 ratio, why?
33. Alkaline earths + halogen = MX2 1:2 ratio, why?
34. alkali + group 16 = M2X 2:1 ratio, why?
35. alkaline earth + group 16 = MX 1:1 ratio, why?
36. All elements with atomic 84 and higher have no stable isotopes. They are radioactive.