Catalyst: The Springfield Nuclear Power Plant has discovered a new element called Homerium (Hm). Element Homerium (Hm) is located between sodium (Na) and potassium (K) on the periodic table. This new Element Hm has a…

A) higher atomic mass than sodium (Na). B) lower atomic number than sodium (Na). C) higher atomic number than potassium (K). D) Hiigher atomic mass than potassium (K).

Update T of C:

25-26 – Building an Atom 27-28 – Periodic TrendsHW: Quiz #2 Mon/Tues on Periodic TrendsWord of the Day: Periodic Trends

Elements are classified by1) metals, nonmetals, and semimetals.

2) Groups or families. (Group 1A, 2A, 3A)

3) Increasing atomic # or # of protons (NOT MASS!)

Or Semimetals

Color Code: Exception Hydrogen is a nonmetal

Metals are 1) Good conductors of heat and electricity. (Conductors- transfer matter)

2) Found on the left side of the periodic table

Exception: Hydrogen (it’s a nonmetal)

Nonmetals are

1) poor conductors (insulators – don’t transfer matter) .

2) Found on the right side of the PT

Semimetals are1) In between metals and nonmetals on the PT, and have properties of both metals and nonmetals.

2) Touching the staircase with the exception of Al and Po. There are 7 of them: B, Si, Ge, As, Sb, Te, At.

Si

Ge

Te

Review Families of the Periodic Table

Alkali MetalsFound in column 1A of the periodic table.

They form 1+ ions by losing their one valence electron to satisfy the octet rule

They react rapidly with water (H2O)

Remember the explosions video clip?

2Na + 2H2O H2 + 2NaOH

Alkaline Earth Metals

Are found in 2A family/column

form 2+ ions in their compounds to satisfy the octet rule.

They may lose their two valence electrons.

Ca + 2H2O H2 + Ca(OH)2

Halogens

These elements always form -1 ions. They each have 7 valence electrons so they tend to gain one electron to satisfy the octet rule.

The Noble Gases

Fully stable, satisfy the octet rule, and are typically unreactive.

Xe

He

More on Halogens

Halogens that exist with a twin of itself are called diatomic elements.

Cl2

F2

O2

Trends in the Periodic Table

Trends in size, ionization energy, and electronegativity.

.

Memorize!

Increasing Atomic Size or Atomic Radius

Increasing Ionization Energy,

and Electronegativity

Size matters

The size (radius) of an atom increases from right to left and up to down.

But why?

Think-pair-share

Remember:

Periods are horizontal rows.

Groups or families are vertical columns.

Trends in Size

The size of an atom is due to the size of the electron cloud.

Know that there are attractions between the electrons and protons in the nucleus. (Opposite charges attract.)

Trends in Size

Across:Atoms get smaller because there are more protons pulling the electrons toward itself making the size of the atom smaller.

Down:The atoms get larger because there are more layers of electrons; more orbits.

Each layer is further from the nucleus so there is less attraction between the nucleus and the valence electrons.

More protons

More layers

Sizes of Ions

Each time an e- is removed, the ion becomes smaller because the nucleus can now further pull electrons toward itself making the ion smaller.

Atoms that gain electrons become larger because the more electrons, the harder it is for the protons in the nucleus to attract those extra electrons.

Electron Shielding Effect Electron Shielding Effect – Valence – Valence electrons become shielded from the electrons become shielded from the positively charged nucleus as you add positively charged nucleus as you add more electron orbits. This effect allows the more electron orbits. This effect allows the atomic radius to increase moving down atomic radius to increase moving down the periodic table.the periodic table.

HONORS ONLY

Ionization Energy

This is the amount energy needed to remove an electron.

It is easier to remove an electron from a larger atom because the electron is farther from the nucleus and feels less attraction.

If it’s easy to remove an e, would there be a high or low IE?

Low IE b/c less energy is required to remove an electron.

Try on own, share with partner after. Order the elements from smallest to largest

IE: potassium, cesium, lithium.

Try again on your own, then talk: Order the elements from largest to smallest

IE: Fluorine, Carbon, Oxygen.

Putting it All Together!

With your table, create a table or graphic organizer on the 2 Periodic Trends learned so far:

It must include: The trend as you go across a

period and down a group. The definition of each trend How nuclear charge impacts

each trend How the number of orbits

impacts the trends An example, using elements, of

how it changes across a period and down a group.

HONORS ONLY

1. Order the following elements from smallest atomic radius to largest atomic radius: Arsenic, Gallium, Germanium.

2. Which element has a larger ionization energy, fluorine or selenium?

3. Why does germanium have a higher ionization energy than lead?

EXIT TICKET

Electronegativity

Electronegativity Electronegativity is the measure of the

ability of an atom to attract electrons.

Electronegativity Trends As you go up a group, the

electronegativity of an element increases.

As you go across a period towards the right, the electronegativity of an element increases.

Why Electronegativity Decreases Down a Group As you go down a group more orbits

are added. Electron Shielding – Valence electrons

become shielded from the positively charged nucleus as you add more orbits.

Electroneg. decreases because there is a decreased ability of the nucleus to attract electrons because of larger distance.

Why Electronegativity Increases Across a Period

As you move to the right, you add more protons.

The more protons, the attracted the electrons to the nucleus so it’s harder for electrons to be removed so elements must have a high electronegativity as you move to the right.

By yourself, then partner talk: Order the elements from smallest to largest

electronegativity: oxygen, beryllium, lithium,

Try again Order the elements from largest to smallest

electronegativity: chlorine, bromine, fluorine

Memorize!

Increasing Atomic Size or Atomic Radius

Increasing Ionization Energy,

and Electronegativity

Exit Ticket1. Define atomic radius2. Define electronegativity.3. Order from largest to smallest electronegativity: Ca, Se, Ni 4. Order from smallest to largest atomic radius: O, Po, S