# Chapter 6.

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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.

Periods 7 rows Each row corresponds to an energy level.

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

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

Measured by finding the size of two of the same elements joined together divided by 2. Measured in picometers (pm) m 1 x m

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

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

Measured by finding the size of two of the same elements joined together divided by 2. Measured in picometers (pm) m 1 x m

Atomic radius decreases across a period

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.

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.

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

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

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.

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.)

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

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

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.

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