MYP Chemistry Topic Periodic Trends Revision Notes

This site uses cookie tracking technologies. Learn more in our Cookie Policy.

MYP Chemistry Topic Periodic Trends Revision Notes | RevisionDojo

Atomic Properties Change Predictably Across Periods and Down Groups

Many atomic properties change in regular patterns as you move across a period (left to right) or down a group (top to bottom) in the periodic table.
Three key properties you should know are:
1. Atomic radius
2. Ionization energy
3. Electronegativity
These trends help explain why some elements are more reactive than others.

Atomic Radius

Atomic radius is a measure of the size of an atom.
It is often defined as half the distance between the nuclei of two bonded atoms of the same element.

Analogy

You can also think of it more simply as the distance from the nucleus to the outermost electrons.

Atomic Radius Increases Down a Group

As you move down a group in the periodic table:

Atoms gain more electron shells, so the distance between the nucleus and the outer electrons increases.
The nuclear charge (number of protons) increases, but this effect is partly cancelled by extra inner electron shells, which provide shielding.
Because of greater shielding and larger distance, the outer electrons are held less tightly.

Therefore, atomic radius increases down a group.

Example

In Group 1:

Lithium (Li) has a smaller atomic radius than cesium (Cs).
Cesium has more electron shells, so its atoms are much larger.

Atomic Radius Decreases Across a Period

As you move across a period from left to right:

The number of protons in the nucleus increases → stronger nuclear charge.
Electrons are added to the same main energy level (same shell).
There is little or no increase in shielding from inner shells.

The stronger nuclear attraction pulls the outer electrons closer to the nucleus, so the atomic radius decreases across a period.

Ionization Energy

Definition

Ionisation energy

Ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms.

Note

For MYP, you can think of it as how much energy it takes to remove an outer electron from an atom.

Ionization Energy Decreases Down a Group

As you move down a group:

Outer electrons are farther from the nucleus.
There are more inner shells, so shielding increases.
The attraction between the nucleus and the outer electrons is weaker.

This means it is easier to remove an electron, so ionisation energy decreases down a group.

Example

As you move down a group:

Outer electrons are farther from the nucleus.
There are more inner shells, so shielding increases.
The attraction between the nucleus and the outer electrons is weaker.

This means it is easier to remove an electron, so ionisation energy decreases down a group.

Ionization Energy Increases Across a Period

As you move across a period from left to right:

The nuclear charge increases (more protons).
Electrons are added to the same shell, so shielding remains similar.
The attraction between the nucleus and the outer electrons becomes stronger.

Therefore, it becomes harder to remove an electron, and ionisation energy increases across a period.

Example

In Period 2:

Fluorine (F) has a higher ionisation energy than lithium (Li).
Fluorine has a greater nuclear charge and a smaller atomic radius, so its electrons are held more tightly.

Electron Affinity

Definition

Electron affinity

Electron affinity is the energy change when one mole of electrons is added to one mole of gaseous atoms, forming one mole of gaseous 1− ions.

Note

For MYP, you can think of it as how much an atom “wants” to gain an electron.

Tip

Electron affinity can be exothermic (energy released) or endothermic (energy absorbed).
In many textbooks, a “more negative” electron affinity means the atom gains an electron more readily.

Electron Affinity Becomes More Negative Across a Period

As you move across a period from left to right:

The nuclear charge increases (more protons).

Nice try, unfortunately this paywall isn't as easy to bypass as you think. Want to help devleop the site? Join the team at https://revisiondojo.com/join-us. exercitation voluptate cillum ullamco excepteur sint officia do tempor Lorem irure minim Lorem elit id voluptate reprehenderit voluptate laboris in nostrud qui non Lorem nostrud laborum culpa sit occaecat reprehenderit

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Duis aute irure dolor in reprehenderit

Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit.

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

MYP Chemistry Periodic Trends Notes

Atomic Properties Change Predictably Across Periods and Down Groups

Atomic Radius

Atomic Radius Increases Down a Group

Atomic Radius Decreases Across a Period

Ionization Energy

Ionization Energy Decreases Down a Group

Ionization Energy Increases Across a Period

Electron Affinity

Electron Affinity Becomes More Negative Across a Period

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Atomic Properties Change Predictably Across Periods and Down Groups

Atomic Radius

Atomic Radius Increases Down a Group

Atomic Radius Decreases Across a Period

Ionization Energy

Ionization Energy Decreases Down a Group

Ionization Energy Increases Across a Period

Electron Affinity

Electron Affinity Becomes More Negative Across a Period

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Periodic table5 subtopics

Matter5 subtopics

Types of chemical reaction18 subtopics

International Union of Pure and Applied Chemistry (IUPAC)4 subtopics

Pure and impure substances2 subtopics

The atmosphere2 subtopics

Bonding4 subtopics

MYP Chemistry Periodic Trends Notes

Periodic table5 subtopics

Matter5 subtopics

Types of chemical reaction18 subtopics

International Union of Pure and Applied Chemistry (IUPAC)4 subtopics

Pure and impure substances2 subtopics

The atmosphere2 subtopics

Bonding4 subtopics

Atomic Properties Change Predictably Across Periods and Down Groups

Atomic Radius

Atomic Radius Increases Down a Group

Atomic Radius Decreases Across a Period

Ionization Energy

Ionization Energy Decreases Down a Group

Ionization Energy Increases Across a Period

Electron Affinity

Electron Affinity Becomes More Negative Across a Period

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Atomic Properties Change Predictably Across Periods and Down Groups

Atomic Radius

Atomic Radius Increases Down a Group

Atomic Radius Decreases Across a Period

Ionization Energy

Ionization Energy Decreases Down a Group

Ionization Energy Increases Across a Period

Electron Affinity

Electron Affinity Becomes More Negative Across a Period

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account