Name: ______Answer Key______Date:______Period: _____
Study Guide – UNIT 6 Quiz – History of the Periodic Table & Trends – ANSWER KEY
Classifying the Elements
The elements can be classified in two ways:
r Metals, non-metals, and semi-metals
r Chemical families (groups)
Label the following on your periodic tables:
r Metals, Non-metals, Metalloids (Semi-Metals)
r s, p, d, & f blocks (use p. 139 to help you)
r Group #s (vertical columns) & Period #s (hor. rows)
r Alkali metals (Group 1), Alkaline Earth Metals (Group
2), Transition Metals (d-block), Halogens (Group 7A
or 17), Noble Gases (Group 8A or 18), Lanthanides
(1st row f-block), and Actinides (2nd row f-block)
r Charges of Groups 1-2, 13-17 (1A=+1, 2A=+2, 3A=+3,
4A=+ or – 4, 5A=-3, 6A=-2, 7A=-1, 8A=0, no charge)
Metals
1. Metals are good conductors of heat and electricity. They are shiny and lustrous. They are malleable which means they can be pounded into thin sheets. They are ductile which means they can be drawn into wires.
2. Metals have low ionization energies_ which means that they do not hold onto their valence electrons tightly. In their compounds they form ions with + charge, called cations.
Nonmetals
3. Nonmetals are poor conductors of heat and electricity. An important exception is pure carbon in the form of graphite. Unlike metals, as solids they are brittle when hit with a hammer.
4. Note that H is a nonmetal even though it is located with the metals on the periodic table.
5. Nonmetals have high ionization energies tightly hold onto their valence electrons. In their compounds they form ions with a - charge, called anions.
Metalloids (Semimetals)
6. Semimetals have properties that are in between metals and nonmetals. They are important in the semiconductor and computer industries. The semimetals are: B Si Ge Sb Te Po and sometimes As
Note: Al and Po are metals. At is a nonmetal.
Alkali Metals (1A): Li Na K Rb Cs Fr
7. In their compounds they always form +1 ions.
8. They react with H2O to form H2(g) and OH-.
9. Their chemistry involves losing (gaining/losing)
one electron. They have one valence electron.
10. They are soft metals and can be cut with a knife.
11. They are never found uncombined in nature
because they are so reactive.
12. They have electron configurations ending s1.
Alkaline Earth Metals (2A): Be Mg Ca Sr Ba Ra
13. In their compounds they always form +2 ions.
14. They slowly react with H2O to form hydrogen
gas and & OH-.
15.Their chemistry involves losing (gaining/losing)
two electrons. They have 2 valence electrons.
16. They have electron configurations ending s2.
Transition Metals (3B – 2B or 3 – 12)
17. These d-block elements are more/less
reactive than alkali & alkaline earth metals.
18. Transition metals usually form + ions, but some, such as palladium, platinum, and gold are among the least reactive of all the elements.
19. These metals can form ions of more than one charge. For example, Cu can be +1 or +2.
Groups (3A – 8A or 13 - 18)
20. You need to know the names of each family in the p – block & how to determine their valence electrons.
Halogens (7A or 17): F Cl Br I At
21. In their compounds they always form -1 ions.
22. They have 7 valence electrons.
23. They react with metals to form
salts which gives them their name of
“salt formers.”
Example: 2 Na + Cl2 ® NaCl
26. Their chemistry involves gaining (gaining/losing) one electron.
Noble Gases (8A or 18): He Ne Ar Kr Xe Rn
24. These elements do not easily combine with
other elements. They are odorless, colorless
and therefore were difficult to discover.
Lanthanides & Actinides
25. These f-block elements are wedged between
groups 3 & 4 in the 6th & 7th periods.
26. Lanthanides are similar to Group 2 elements.
27. The actinides are all radioactive. The first 4 (Th-Np) have been found naturally on earth; the remaining are known only as laboratory made.
Hydrogen, H
28. Hydrogen is its own family because it has properties that don’t resemble other groups.
29. It usually forms +1 ions, but can also form -1.
30. Hydrogen is located with the alkali metals family, but it is in fact a metal/nonmetal.
Helium, He
31. Helium is positioned with the Noble Gases
32. Although it does not have a full octet of outermost electrons, its 1s orbital is full, a duet.
33. Helium is considered part of the s block.
Trends in the Periodic Table
There are four main trends which you must know about when it comes to the periodic table. For example, do atoms of elements increase as you go across the table, or decrease? What about as you go down the table? The four you need to know are:
(1) Atomic Radii, (2) Ionization Energy,
(3) Ionic Radii, and (4) Electronegativity
(1) Atomic Radii (Sizes of Elements) Fig. 13, p. 151
34. The size of an atom is equal to the size of the atomic radius.
35. The two forces at play are repulsion between electrons and other electrons and attraction between the electrons and protons in the nucleus.
36. Left to right across the table, the atoms get smaller because there are more and more protons in the nucleus pulling on the valence e-.
37. Going down any group or family, the atoms get larger because there are more and more layers of electrons. Each level of electrons is farther from the nucleus.
> > > Atomic radius decreases across table ®
Atomic radius
increases
down table ¯
(Sketch the trend in Atomic Radii)
(2) Ionization Energy (IE) Figure 15, p. 153
38. This is defined as the energy needed to remove an electron from an atom.
39. It is easier (easier/harder) to remove an electron from a larger atom.
40. This is because the electron is farther (closer/farther) from the nucleus & feels less (less/more) attraction.
41. Each time an electron is removed, the atom/ion becomes smaller, and it becomes harder (harder/easier) to remove the e-.
42. This means it takes a higher (higher/lower) IE to remove each successive electron.
43. The trend in IE is the opposite of atomic radii.
> > >I.E. increases across table ®
I.E.
decreases
down table
¯
(Sketch the trend in Ionization Energy)
(3) Ionic Radii (Sizes of Ions) Figure 19, p. 159
44. The word “ion” means charge.
45. When an atom loses electrons, it becomes a + charge, and is known as a cation.
46. When an atom gains electrons, it becomes a - charge, and is known as a anion.
47. Each time an electron is removed, the atom/ion
becomes smaller (smaller/larger) because
there is less (more/less) e-/e- repulsion.
48. Each time an electron is added, the atom/ion becomes larger (smaller/larger) because there is more (more/less) e-/e- repulsion.
49. Generally, the trend in ionic radii is the
same as atomic radii.
> > > Ionic radii decreases across ®
Ionic radii
increases
down ¯
(Sketch the trend in Ionic Radii)
(4) Electronegativity (Popularity) Fig. 20, p. 161
50. Electronegativity is defined as the ability of an
atom to attract electrons to itself.
51. The trends in electronegativity follow the trends in ionization energy.
> > > Electronegativity increases across ®
Electro.
decreases
down ¯
(Sketch the trend in Electronegativity)
Summary of 4 Trends
52. Atomic radii and ionic radii decrease as you go
across, and increase as you go down.
53. IE and electronegativity increase as you go
across, and decrease down the periodic table.
Scientists of the Periodic Table
Know the six scientists who contributed to the development of the periodic table. Know how they arranged/rearranged the table. Be able to compare/contrast them!