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Parts 03PeriodicTrends

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1. Periodic Trendsa. Atomic Radius

- distance from the nucleus to the last energy level

- measured in pm

Li3

73 p+

4 no

2 e- 1 e-

1st2nd

atomic radius

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Li1 e-

Fr

1 e-

As atomic numberincreases, down a group, atomic radius increases. The increased charge of the nucleus pulling in the energy levels is not enough to overcome the increasing size caused by the added energy levels.

atomic radius

atomic radius

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Li1e-

Ne8e-

As atomic number increases across a period, atomic radius decreases. Because the number of energy levels does not increase, the increased charge of the nucleus pulling in the energy levels causes the energy levels to move closer to the nucleus and the atomic radius decreases.

atomic radius atomic radius

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a. Atomic RadiusDown a group, atomic radius increases.Across a period, atomic radius decrease.

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1. Periodic Trendsb. Formation of Ions

- an ion is a charged particle- a cation is a positively charged

particle- metal atoms form cations by

losing e’- a cation is always smaller than

its atom- an anion is a negatively charged

particle- nonmetal atoms form anions

gaining e’- an anion is always larger than

its atom

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1123Na 1e-

11 p+12 no 2e- 8e-

Sodium Atom

11 +11-0 Neutral:

no net charge

0

Loses itsone valence electronto get astable octet 11

23Na 11 p+12 no 2e- 8e-

11 +10-1+ Cation:

Positivelycharged

1+

Sodium Ion

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Alkali Metals (group I)Very reactive! Reacts with water to form hydrogen and a base. So reactive, they are not found as an atom in nature. Reactivity increases down the group. Only found in compounds. Stored under oil due to possibility of reacting with water in the air.

Alkaline Earth Metals (group II)Similar to group I. Less reactive. Not as soft. Denser. Carbon group (group IV)Can give or take 4 e-. Carbon can exist in two different physical forms.When elements can do this the forms are called ALLOTROPES.What are the two forms of Carbon?Diamond and graphiteOxygen can exist as O2 and O3. O3 is called? Ozone

Halogen group (group VII)

Most reactive nonmetals with F being the most reactive element. They Lose one e- to gain a stable octet.

Noble gases (group VIII)

Chemically stable (inert). All are undetectable by human senses.

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1224Mg 2e-

12 p+12 no 2e- 8e-

Magnesium Atom

12 +12-0 Neutral:

no net charge

0

Loses itstwo valence electronsto get astable octet12

24Mg 12 p+12 no 2e- 8e-

12 +10-2+ Cation:

Positivelycharged

2+

Magnesium Ion

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1327Al 3e-

13 p+14 no 2e- 8e-

Aluminum Atom

13 +13-0 Neutral:

no net charge

0

Loses itsthree valence electronsto get astable octet13

27Al 13 p+14 no 2e- 8e-

13 +10-3+

3+

Aluminum Ion

Cation:Positivelycharged

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1531P 5e-

15 p+16 no 2e- 8e-

Phosphorus Atom

15 +15-0 Neutral:

no net charge

0

Gains three electronsto get astable octet

Anion:Negativelycharged

1531P 15 p+

16 no 2e- 8e- 8e-

15 +18-3-

Phosphide Ion

3-

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1632S 6e-

16 p+16 no 2e- 8e-

Sulfur Atom

16 +16-0 Neutral:

no net charge

0

Gains two electronsto get astable octet

Anion:Negativelycharged

1632S 16 p+

16 no 2e- 8e- 8e-

16 +18-2-

Sulfide Ion

2-

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1735Cl 7e-

17 p+18 no 2e- 8e-

Chlorine Atom

17 +17-0 Neutral:

no net charge

0

Gains one electronto get astable octet

Anion:Negativelycharged

1735Cl 17 p+

18 no 2e- 8e- 8e-

17 +18-1-

Chloride Ion

1-

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b. Oxidation Numbers: Charges of Ions

1+

2+

Variable Oxidation Numbers

Usually 2+

3+

4+-3-2-1-0

2+2+1+ 2+

or4+

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c. Ionization EnergyEnergy needed to remove one electron

from the element in its isolated gaseous state

X(g) + 1 e-IE X1+(g) +

Rb(g) + 1 e-IE Rb1+(g) +

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1632S 6e-

16 p+16 no 2e- 8e-

Sulfur Atom

16 +16-0 Neutral:

no net charge

0

IonizationEnergy removesone electronfrom the lastenergy level16

32S 16 p+16 no 2e- 8e- 5e-

16 +15-1+

Positive Ion

1+

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c. Ionization EnergyDown a group, ionization energy decreases.The atoms get larger so it is easier to remove 1e-.

Across a period, ionization energy increases.The atoms get smaller so it is more difficult to remove

1e-.

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Examples:What element has the smallest atomic radius in group II?BerylliumWhat element has the largest ionization energy in group VI?Oxygen

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Examples:What element has the largest atomic radius in Period 4?PotassiumWhat element has the highest ionization energy in Period 5?Xe

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Examples:What is the oxidation number of radium?2+What is the oxidation number of selenium?2-What is the oxidation number of gallium?3+What is the oxidation number of iodine?1-

Assignment p.58-68… p. 69-70 will be extra credit on the test.