The Periodic Table and Periodicity

In our last class... We examined 4 different groups (or families)  the Alkalai Metals (Group 1)  the Alkaline Earth Metals (Group 2)  the Halogens (Group 17)  the Noble Gases (Group 18)

In our last class... We also looked at 3 different classes of elements  the Lanthanides and Actinides (4f, 5f or the inner Transition Metals)  the Transition Metals (the d block, 3d, 4d, 5d, 6d)  the Metalloids (B, Si, P, As, Se, Te) While the chemistry of the elements in the d and f blocks is very rich we don’t examine it much more in this course. We devote much of our attention to the s block (Groups 1 and 2) and the p block (Groups 13 – 18). Yesterday we looked at some interesting features of the metalloids, the halogens and the noble gases, today we will examine the rest.

Increasing Electronegativity Increasing Effective Nuclear Charge

What element is the easiest to ionize (make a +1 cation)? Which non-noble gas element is the least metallic? Which is larger Chlorine or Bromine? Which is more metallic, Pd or Pt? Fr Fluorine Bromine Platinum

In our upcoming unit on Chemical Bonding we will only be examining the elements of the s and p blocks. Therefore we need to address the new term VALENCE. Valence refers to the number of electrons an atom has in its outermost layer. Furthermore the maximum number of valence electrons an atom (remember just the s and p blocks now) can have is 8. (Groups 1, 2, 13, 14, 15, 16, 17, 18) It’s the valence electrons that are used to bond with other atoms.

Consider Be and O: Be has e - configuration: 1s 2 2s 2, because the highest energy level (n = 2) has 2 electrons in it, we say Be has 2 valence electrons. O has e - configuration 1s 2 2s 2 2p 4, because the highest energy level (n = 2) has 6 electrons in it, we say O has 6 valence electrons. How many valence electrons does P have? Does Sb have? Does As have? 5 How many valence electrons does Ga have? Does Al have? Does B have? 3 What do you notice? Atoms of the same group have the same number of valence electrons.

We will use the Lewis Dot Method 1.Valence electrons (up to 8) are represented as dots around the element’s symbol 2.We draw up to 4 e - as “singles” then the next 4 are paired up Group # # of valence electrons

The Boron Family Group 13 contains: B, Al, Ga, In and Tl. Each element has 3 valence electrons. Electronic configurations of 2s 2 2p 1, 3s 2 3p 1 etc. Boron is a metalloid, the rest are considered metals. The elements of Group 13 typically form compounds with H and the non-metals (light blue).

The Carbon Family Group 14 contains: C, Si, Ge, Sn, and Pb. Each element has 4 valence electrons. Electronic configurations of 2s 2 2p 2, 3p 2 3p 2 etc. Carbon readily forms 4 bonds. This versatility is the basis for its presence in living things. The elements of Group 14 typically form compounds with H and the non-metals (light blue). Silicon (metal) Silicone (polymer)

Group 15 contains: N, P, As, Sb and Bi. Each element has 5 valence electrons. Electronic configurations of 2s 2 2p 3, 3p 2 3p 3 etc. Nitrogen and the rest of Group 15 readily from 3 bonds (we will examine in detail later). The elements of Group 15 typically form compounds with H and the non-metals (light blue). The Nitrogen Family The active medicinal ingredient in Pepto- Bismol is bismuth. Based on the other metals in its family and around it why is this weird?

Group 16 contains: O, S, Se, Te and Po. Each element has 6 valence electrons. Electronic configurations of 2s 2 2p 4, 3p 2 3p 4 etc. Oxygen and the rest of the group readily form 2 bonds. Oxygen and Sulfur form bonds with other non- metals but also readily with metals. When a metal reacts with oxygen we use the term oxidation. The Oxygen Family Iron, Fe Rust, Fe 2 O 3

Group 17 contains: F, Cl, Br, I and At. Each element has 7 valence electrons. Electronic configurations of 2s 2 2p 5, 3p 2 3p 5 etc. Group 17 usually only form 1 bond with another element. These non-metals typically form compounds with metals. The Halogens Table salt, NaCl Fluoride, NaF or H 2 SiF 6

Increasing Electronegativity Increasing Effective Nuclear Charge

Complete the Periodic Table Detectives Activity. You may use your notes, your textbook or ask me to flip to any slide in either yesterday or today’s presentation.