Periodic Table Notes Unit 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 Atoms Bonding 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