Trends of the periodic table

Trends of the periodic table

Trends of the periodic table are things that occur regularly across the table.

Reminder!!

• Periods are the horizontal rows of the table

• Groups (or families) are the vertical columns of the table.

Atomic Radii

• This is how big the atom is.

• The size of an atom decreases as you move across a period

• The radii increases as you move down a group

Atomic Radii

• If we look at group 1

• Lithium (Li 3) is smaller in radii than Francium (Fr 87)

Atomic Radii

• If we look at period 2

• Lithium (Li 3) is larger in radii then Florine (F 9)

Multiple Choice

What is a group in the periodic table?

• A column of the table (vertical)

• A row of the table (horizontal)

Multiple Choice

What is a period in the periodic table?

• A column of the table (vertical)

• A row of the table (horizontal)

Multiple Choice

What would have a larger radius: Calcium (Ca 20) or Barium (Ba 56)

• Ca

• Ba

Atomic Radii

• The reason atomic radii decreases as you move left to right in a period is because of the increasing number of protons in the nucleus.

• A proton has a great effect on an electron pulling them closer to the center and decreasing the radius of the atom.

Atomic Radii and Electron shielding

• Remember when we talked about repulsion and attraction. Like charges ( two positives or two negatives) repel each other (or push each other apart) while two opposite charges attract each other.

Atomic Radii and Electron shielding

• Electrons in inner energy shells do two things that we refer to as electron shielding

• They push against the electrons outside of them because two like charges repel

• When they are between the nucleus and an outer electron they temporarily decrease the effect of attraction between the nucleus and the outer electron

Atomic Radii and Electron shielding

• Electron shielding causes electrons further out from the nucleus to not be as pulled in as they could be allowing the radius of the atom to be big.

Atomic Radii

• As we move down a group more and more electrons are being added to the further out energy shells.

• Because of this, they are not held in as tight due to electron shielding so the radius increases as you move down a group.

Multiple Choice

What is electron shielding?

• Where electrons play war games

• Where electrons attract each other from the nucleus

• Where electrons push each other away and temporarily block the attraction of the nucleus resulting in a decrease effect of the nucleus.

• Where electrons push each other away and out of the atom

Multiple Choice

What is the cause of the increase in atomic radii as you move down a group?

• More electrons and electron shielding causes the electrons to be as wide as possible.

• More electrons and electron shielding causes the electrons to be pulled in as much as possible.

Multiple Choice

What causes the smaller atomic radii as you move from left to right in a period?

• Strong nuclear attraction and minimal electron shielding

• Strong nuclear attraction and strong electron shielding

• Minimal nuclear attraction and minimal electron shielding

Ionization energy

• Ionization energy is the amount of energy that is required to remove an electron from an atom

• As you remove electrons more and more energy is required to remove another.

Ionization energy

• Ionization energy increases as you move from left to right in a period

• It also decreases as you move from top to bottom of a group.

• This is the opposite of atomic radii but because of the same reasons

Ionization energy

• Atoms with small atomic radii have those because the nucleus has such a strong pull on its electrons.

• This is due to having a lot more protons then the left side of the table but no increase in electron shielding

Ionization energy

• Because of the strong pull, it would take more energy to remove an electron from the upper right of the periodic table than the bottom left of it.

• The noble gases have some of the highest ionization energy.

• Francium (Fr 87) and Cesium(Cs 55) has some of the lowest ionization energy

Multiple Choice

What is ionization energy?

• Electrons blocking other electrons

• Energy needed from a nucleus to hold on to a prton

• Amount of energy needed to remove an electron from an atom.

• The amount of energy needed to remove a proton

Electronegativity

• Electronegativity is a number that represents an atom's ability to attract electrons to it.

• Its trends match those of ionization energy

• Increases from left to right in a period

• Decreases from top to bottom in a group

Electronegativity

• Some atoms such as high electronegativity (Oxygen, Florine, Chlorine) they have enough energy to take an electron from another atom.

• In order for an atom to take an electron, it has to have high electronegativity and the atom it is taking an electron from has to have low electronegativity

Electronegativity

• For example, Chlorine (Cl 17) has enough energy to pull an electron off of Sodium (Na 11).

• This forms a compound we use every day... table salt.

Multiple Choice

What is electronegativity?

• A number that represents the ability of an atom to attract an electron to itself

• The amount of energy needed to remove an electron

• The ability of an atom to eject an electron

• The ability of an atom to hold onto a proton

To review

• Atomic radii decrease from left to right but increase from top to bottom

• Ionization energy and electronegativity increase from left to right and decrease from top to bottom

• Most of the trends we see are because of the interaction between the number of protons in the nucleus and electron shielding

Multiple Choice

What trend do ionization energy and electronegativity follow?

• The increase from left to right and decrease from top to bottom

• The decrease from left to right and decrease from top to bottom

• The increase from left to right and increase from top to bottom

• The decrease from left to right and increase from top to bottom