PERIODIC TRENDS AND THE PERIODIC TABLE

Transcription

1 PERIODIC TRENDS AND THE PERIODIC TABLE

2 THE PERIODIC TABLE The row tells us how many energy levels are in that atom The row is also the group The column tells us how many electrons are in the outer energy level *Electrons in the outer energy level are called valence electrons The column is also the family

3 ELEMENT FAMILIES Column 1 A Alkali Metals React violently with water! One valence electron Column 2A Alkali Earth Metals Two valence electrons Column 7 A Halogens 7 valence electrons Column 8A Noble Gases 8 valence electrons Do not react! ( inert )

4 METALS, NONMETALS, METALLOIDS

5 QUICK CHECK 1. Which element is a metal, has five energy levels, and two valence electrons? 2. Which element is a nonmetal, has two energy levels, and four valence electrons? 3. What are the electron configurations?

6 1. Sr [Kr] 5s 2 2. C [He] 2s 2 2p 6 QUICK CHECK

7 THE OCTET RULE Atoms will gain, lose, or share electrons in order to have eight electrons in their outer energy level, giving them the same electron configuration as a noble gas Atoms are most stable with eight valence electrons

8 PERIODIC TRENDS Charges (oxidation numbers) have a pattern with the periodic table Example: How many valence electrons does Mg have? To follow the octet rule, Mg needs to either: Gain six electrons Lose two electrons Which is easier? Losing two!

9 PERIODIC TRENDS Now Magnesium has the same electron configuration as Neon. (yay!) BUT, if Magnesium still has 12 protons, and now only has 10 electrons, what is its charge? Mg 2+

10 PERIODIC TRENDS Atoms with 3 or fewer valence electrons tend to lose electrons Atoms with 5 or more valence electrons tend to gain electrons Example: Predict Oxidation numbers for: Al Ca O Br

11 PERIODIC TRENDS Example: Predict Oxidation numbers for: Al lose 3 electrons 3+ Ca lose 2 electrons 2+ O gain 2 electrons -2 Br gain 1 electron -1

12

13 ELECTRON CONFIGURATION BATTLESHIP Make a board with 1 5-square 1 4-square 2 3-square 1 2-square You must call out the electron configuration (noble gas abbreviations) for a hit or a miss Mark an x for hit and o for miss Each person must make at least 10 calls!

14 TRENDS IN ATOMIC SIZE atomic radius Increases as you go down the periodic table Decreases as you move left to right Atoms get heavier More positive charge pulls electrons tighter

15 TRENDS IN ATOMIC SIZE Arrange in order of decreasing atomic size: Mg, S, Si, Al, P Arrange in order of increasing atomic size: F, I, Br, At, Cl Mg, Al, Si, P, S F, Cl, Br, I, At

16 TRENDS IN IONIZATION ENERGY Energy required to remove the outer most electron How much does the atom want to keep its outer electron?

17 TRENDS IN IONIZATION ENERGY Ionization energy increases from left to right Metals want to lose electrons to follow the octet rule, so it takes less energy to take them away Nonmetals want to gain electrons they are unwilling to give them away! Ionization energy increases from bottom to top The closer you get to the nucleus, the more the electrons are attracted to it

18 TRENDS IN IONIZATION ENERGY Noble gases have the highest ionization energies Alkali metals have the lowest ionization energies

19 TRENDS IN IONIZATION ENERGY Why does the graph drop down in certain places?? Half full or full sublevels are most difficult to remove electrons

20 TRY THESE Which has the greatest energy level? Fe, Ca, Se Rb, Na, Cs Se! Na!

21 WHY IS THERE A DECREASE IN IONIZATION ENERGY WHEN YOU MOVE FROM PHOSPHORUS TO SULFUR? Orbital Filling! Phosphorus is p3, Sulfur is p4 Orbitals prefer to be half full.

22 TRENDS IN ION SIZE When atoms turn into ions, they change size due to adding/losing electrons When an atom LOSES an electron, the ion becomes SMALLER The protons pull in the remaining electrons more (positive ions are smaller than their atoms) When an atom GAINS an electron, the ion becomes LARGER The protons have to attract more electrons that usual (negative ions are larger than their atoms)

23

24 TRENDS IN ELECTRONEGATIVITY Tendency for atoms to attract electrons even when they are chemically bonded

25 TRENDS IN ELECTRONEGATIVITY Increases left to right, bottom to top Noble gases have no electronegativity!

26 QUICK CHECK Which element would have the greatest electronegativity: C, N, or O? Which element would have the lowest electronegativity: Br, Cl, or F? O Br

27 HOMEWORK Book page 186#34, 36, 38, 41, 43-48, 61

28 EXIT QUESTION: DEFINE Octet rule Finding oxidation numbers/charges Atomic size Ionization energy Ion size Electronegativity