1 Periodic Table II Periodic table arranged according to electron arrangement Periodic table also arranged according to properties? Properties must depend on electron arrangement!

2 Periods (horizontal) 1, 2, 3 etc. Elements with same number of occupied energy levelsOR Same outer (valence) energy shell Example: period 3 Elements have electrons in 3 energy levels OR 3 rd level is the valence shell Al: 2 – 8 – 3 Vary from 1 to 8 Val. e - Properties vary as # increases

3 Groups (vertical) 1,2,…18 Elements with similar number of valence electrons or Same number of valence electrons make for similar properties in groups Valence electrons

4

5 Periodic trends How big are atoms? Atomic radius How can You explain These trends? (how do the Structure of atoms differ?

6 Trends in Atomic Radius (size) Radius: ½ the distance between two nuclei Depends on nuclear charge (protons) AND Number of energy levels with electrons (distance)

7 As atomic number increases going down a group each atom has an additional energy level, further from the nucleus. Radius goes UP since the valence shell is now further from the nucleus. As atomic number increases going down a group each atom has an additional energy level, further from the nucleus. Radius goes UP since the valence shell is now further from the nucleus.

8 As Atomic number increases across a period, atoms are gaining more protons in their nuclei (greater nuclear charge) Radius decreases - extra positive charge from the protons pulls the electrons closer to the nucleus Large Small

9 Atomic radiilarger smaller Overall Trend

10

11 Forming an ion: Atoms lose or gain electrons to form ions. Why? Na + = 11 P e- = + 1 charge O 2- = 8 P e - O 2- = 8 P e - = -2 charge = -2 charge Why are some atoms losers, and other atoms gainers? Verystable

12 Mg kJ ---> Mg + + e - Energy Called the FIRST ionization energy because we removed only the OUTERMOST electron Mg kJ ---> Mg 2+ + e- This is the SECOND IE. Takes more energy for the next electron. Why? Energy required to remove an electron from an atom. Indicates how easily an atom loses an electron also. Atomic Strength: Ionization Energy ion and electron

13 2) Na kJ ---> Na + + e - Energy Energy Can you explain this trend in ionization energy? 1) K kJ ---> K + + e - Energy Energy Hint: compare the structures on the right  1 e - in 4 th shell 1 e - in 3 rd shell (“strength” – energy to hold onto outer electrons) Electron is farther away in K so its weaker More protons in K, But…

14 3) Mg kJ ---> Mg + + e - Energy Energy 2) Na kJ ---> Na + + e - Energy Energy Can you explain this trend in ionization energy? 1) K kJ ---> K + + e - Energy Energy (“strength” – energy to hold onto outer electrons) Stronger nuclear charge (# protons) in Mg than Na

15 3) Mg kJ ---> Mg + + e - Energy Energy 2) Na kJ ---> Na + + e - Energy Energy Can you explain this trend in ionization energy? 1) K kJ ---> K + + e - Energy Energy 4) Mg kJ ---> Mg +2 + e - Energy Energy +12 (“strength” – energy to hold onto outer electrons) 1 electron pushes the other 1 electron left, less electrons to push

16 What is this? What does this illustrate? The “key”?

17 Trends in Ionization Energy IE increases across a period because the positive nuclear charge increases (more protons). Metal (left side) weak - lose electrons more easily: losers Nonmetals (right) strong - don’t lose electrons: gainers Ionization energy increases gainers losers losers

18 IE decreases down a group Because size increases: greater distance from nucleus to valence electrons and *Shielding Effect *Each additional energy level adds electrons that repel the valence e - ’s Ionization energy decreases

19 Periodicity: a trend that occurs at regular intervals Overall Trend

20

21 Learning check 1.Which atom is larger; H or He? Why? 2. Which is larger; and argon atom or a potassium atom? Why? 3.Describe the overall trend in atomic radius on the periodic table 4.Which will have a higher ionization energy H or He? Why? 5.Which will have a larger ionization energy Ar or K? Why? 6.Describe the overall trend in ionization energy on the periodic table.

22 Chemical strength: Electronegativity measure of the ability of an atom in a molecule to attract electrons to itself. Attraction for a pair of electrons shared in a chemical bond

23 Electronegativity: same as trends in Ionization energy increases decreases Why no values for group 18? Decreases: MoreEnergyLevels=Weakerforce Increases: stronger nucleus = stronger force

24

25 Which has a higher: 1 st ionization energy? Mg or Ca ? Al or S ? Cs or Ba ? Which is more electronegative? F or Cl ? Na or K ? Sn or I ? Circle one in each pair HDYK? Why?

26 Ionization Energy

27 Introduction to Chemical Reactivity Atoms lose or gain electrons to become stable like group 18 elements (8 valence e - ‘ s) Ex: Ne What’s the magic number?

28 Nonmetals gain To become like Noble gases Metals lose To become Like Noble gases F: 2-7, becomes 2-8 Na: 2-8-1, becomes 2-8 What elements sit beyond group 18?

29 Metals – group 1,2 and transitional, etc. Chemically weak, tend to lose outer electrons to stronger atoms Ex: Mg loses 2e - –becomes like Ne –Becomes a positive ION Mg 2+ –ION = charged “atom” –CATION – a positively charged ion

30 Nonmetals – groups 15, 16, 17 Chemically strong tend to gain electrons from weaker atoms Ex: Fluorine atom F gains 1 e - becomes like Ne Becomes a negative fluoride ION: F 1- ANION - a negative ion gain 1 e -

31

32 37 What is the total number of electrons in a Cu+ ion? (1) 28 (3) 30 (2) 29 (4) When a lithium atom forms an Li+ ion, the lithium atom (1) gains a proton (2) gains an electron (3) loses a proton (4) loses an electron

33 Ion Sizes Which of the following is the smallest: O 2- ion, Ne atom, or Mg 2+ ion? Why? Hint: Each has how many electrons? But: each has how many protons? Neon oxide magnesium

34 Ion Sizes Metal ions are SMALLER than the atoms from which they come. Loss of entire energy level so size DECREASES. Forming a cation.

35 Nonmetal ions are LARGER than the atoms from which they come. Additional electrons repel each other more so size INCREASES (“swells up”) Forming an anion

36 Loser metal

37 F gains e-

38 9 An atom of an element has a total of 12 electrons. An ion of the same element has a total of 10 electrons. Which statement describes the charge and radius of the ion? (1) The ion is positively charged and its radius is smaller than the radius of the atom. (2) The ion is positively charged and its radius is larger than the radius of the atom. (3) The ion is negatively charged and its radius is smaller than the radius of the atom. (4) The ion is negatively charged and its radius is larger than the radius of the atom. Atomic # 12 = Mg 12 P e - Mg lost 2 e - to become like Ne: 3 Energy levels to 2 Energy levels

39 Test your understanding 1.What is the electron configuration for a magnesium atom? 2.In terms of electrons, what will likely happen to magnesium during a chemical reaction? 3.What will be its new electron configuration? 4.Draw the Bohr diagram for the magnesium atom and the magnesium cation. 5.Which will be larger? Why?

40 Activity / Reactivity Metals –”losers” must lose electrons during reactions weakest (lowest electronegativity) are most active (francium) Nonmetals – gainers must gain electrons during reactions strongest (highest electronegativity) are most active (fluorine) F Fr More Active metals More Active nonmetals

41 Metallic / nonmetallic “character” More(gainer)Nonmetalliccharacter More(loser)metalliccharacter

42 33 As the elements in Group 17 on the Periodic Table are considered from top to bottom, what happens to the atomic radius and the metallic character of each successive element? (1) The atomic radius and the metallic character both increase. (2) The atomic radius increases and the metallic character decreases. (3) The atomic radius decreases and the metallic character increases. (4) The atomic radius and the metallic character both decrease. Larger and weaker: more metallic (better “losers”)

43 Hint: standard temperature = 0 0 C For questions 73 – 76 Refer to the table below and your knowledge of chemistry

45 1) How many elements are solids at STP? 2) Which element is a noble gas? 3) Letter Z below corresponds to a different element. Elements G,Q, L and Z are in the same group on the periodic table as shown to the right. 4) Based on the trend in melting points for G, Q and L, estimate the melting point of Element Z

46