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Chapter 6. Periodic Law When elements are arranged in order of increasing atomic #, there is a periodic repetition of their chemical and physical properties.

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Presentation on theme: "Chapter 6. Periodic Law When elements are arranged in order of increasing atomic #, there is a periodic repetition of their chemical and physical properties."— Presentation transcript:

1 Chapter 6

2 Periodic Law When elements are arranged in order of increasing atomic #, there is a periodic repetition of their chemical and physical properties.

3 Periods 7 rows Each row corresponds to an energy level.

4 Groups/Families Vertical columns Elements in the same groups have similar properties. Elements in same group have the same electron configuration for their highest energy level

5 Trend Pattern of behavior. Generally shows a change in a certain direction (increases/decreases, etc.)

6 Periodic Trends Atomic Radius:Atomic Radius: –Radius of 1 atom. –Measured by finding the size of two of the same elements joined together divided by 2. –Measured in picometers (pm) m –1 x m

7 Ionization Energy:Ionization Energy: –The amount of energy required to remove the 1 st electron from an atom. –Measured in kJ/mol

8 Electronegativity:Electronegativity: –The ability of an atom to attract electrons in a compound. –No units

9 Periodic Trends Atomic Radius:Atomic Radius: –Radius of 1 atom. –Measured by finding the size of two of the same elements joined together divided by 2. –Measured in picometers (pm) m –1 x m

10 Atomic Radius: Trend: –Atomic radius increases down a group –Atomic radius decreases across a period

11 Atomic Radius Explanation: –As the number of energy levels increases, the filled energy levels shield the electrons in the outside shell from the attraction of the nucleus. Therefore size increases down a family/group.

12 Atomic Radius Explanation: –The more electrons an element has, the greater the attraction to the positive nucleus so the atom is pulled in tighter and it’s smaller. Therefore size decreases across a row.

13 Ionization Energy:Ionization Energy: –The amount of energy required to remove the 1 st electron from an atom. –Measured in kJ/mol

14 Ionization Energy: Trend: –Ionization Energy decreases as you move down a group. –Ionization Energy increases as you move across a period.

15 Ionization Energy: Explanation: –As you move down a group, the outer electrons are farther away from the nucleus so it is easier to pull them away from the atom. Requires less energy.

16 Ionization Energy: Explanation: –As you move across a period, the positive charge of the nucleus increases and it has a greater pull on the electrons. This makes it harder for them to be pulled away from the atom and ionization energy increases. (They don’t want to give up their electrons.)

17 Electronegativity:Electronegativity: –The ability of an atom to attract electrons in a compound. –No units

18 Electronegativity: Trend: –Electronegativity decreases as you move down a group. –Electronegativity increases as you move across a period.

19 Electronegativity: Explanation: –The stronger electrons are attracted to the nucleus, the higher the electronegativity. –Elements with high ionization energy have high electronegativity  they don’t want to give up electrons, they want to attract them.

20 Electronegativity DECREASES Electronegativity INCREASES Ionization Energy DECREASES Ionization Energy INCREASES Atomic Radius INCREASES Atomic Radius DECREASES Summary of Periodic Trends


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