Periodic Table NotesUnit 3 – Notes

Periodic Table

Nonmetals are on the right side of the periodic table (with the exception of H).

Periodic Table

Metals are on the left side of the chart.

Periodic Table

Metalloids border the stair-step line (with the exception of Al, Po, and At).

Diatomic Molecules

These seven elements occur naturally as molecules containing two atoms.

Ions

• When atoms lose or gain electrons, they become ions.– Cations are positive and are formed by elements on the

left side of the periodic chart.

– Anions are negative and are formed by elements on the right side of the periodic chart.

Development of Periodic Table

• Elements in the same group generally have similar chemical properties.

• Physical properties are not necessarily similar, however.

Development of Periodic Table

Dmitri Mendeleev and Lothar Meyer independently came to the same conclusion about how elements should be grouped.

Metals versus Nonmetals

• Metals tend to form cations.• Nonmetals tend to form anions.

Metals

They tend to be lustrous, malleable, ductile, and good conductors of heat and electricity.

Nonmetals• These are dull, brittle

substances that are poor conductors of heat and electricity.

• They tend to gain electrons in reactions with metals to acquire a noble gas configuration.

Metalloids

• These have some characteristics of metals and some of nonmetals.

• For instance, silicon looks shiny, but is brittle and fairly poor conductor.

Periodic Trends

• In this chapter, we will rationalize observed trends in– Sizes of atoms and ions.– Ionization energy.– Electronegativity

What Is the Size of an Atom?

The bonding atomic radius is defined as one-half of the distance between covalently bonded nuclei.

Measured in nanometers

Nuclear Charge

• The positive charge of the protons

• For example sodium has a nuclear charge of +11

Sizes of AtomsBonding atomic radius tends to… …decrease from left to

right across a row

…increase from top to bottom of a column

Atomic Radius

Ionization Energy

• The ionization energy is the amount of energy required to remove an electron from the ground state of an atom.– The first ionization energy is that energy

required to remove first electron.– The second ionization energy is that energy

required to remove second electron, etc.– Measured in J or kJ

Ionization Energy• It requires more energy to remove each successive

electron.• When all valence electrons have been removed, the

ionization energy takes a quantum leap.

Trends in First Ionization Energies

• As one goes down a column, less energy is required to remove the first electron.– For atoms in the same

group, Zeff is essentially the same, but the valence electrons are farther from the nucleus.

Electronegativity

• A measure of how well you attract electrons.– A scale of 0 – 4– Created by Linus Pauling