Chapter 6The Periodic Table

6.1 Objectives

Explain how elements are organized in a periodic table.

Compare early and modern periodic tables.

Identify three broad classes of elements.

Prior Knowledge

For this unit we will need to recall a few concepts from previous topics. We will need to recall the following: Protons, Neutrons, Electrons, Atomic Number, and Atomic

Mass, as well as how they “work” together.

Electrons configurations, as well as abbreviated configurations (Noble Gas).

Searching For an Organizing Principle

Chemists used the properties of elements to sort them into groups.

J.W. Dobereiner published a system of organizing the elements into triads, or a group of three elements with similar properties.

KEYWORD- TRIADS

Mendeleev’s Periodic Table

The triad method for organizing the elements was flawed, and a new system was needed.

Mendeleev decided to arrange the periodic table in order of increasing atomic mass, as well as into specific groups.

The Periodic Law

Mendeleev noticed that organizing the elements into groups as well as atomic mass created an imperfect order.

In 1913, Henry Moseley was able to determine the atomic number for each known element at that time.

Periods, Groups, and Periodic Law

Periodic Law are when elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties

KEYWORD-PERIODIC LAW

Metals, Nonmetals, and Metalloids

Metals

Metals compose about 80% of the periodic table.

Excellent conductors.

Aside from mercury (Hg), all metals are solid at room temperature.

Ductile and Malleable

KEYWORD- METALS

Nonmetals

Poor conductors, except Carbon

Brittle

Most are gasses at room temperatures, Sulfur and Phosphorus are solid, Bromine is a liquid.

KEYWORD- NONMETALS

Metalloids

Can behave like a metal and nonmetal depending on conditioning.

KEYWORD- METALLOIDS

6.2 Objectives

Describe the information in a periodic table.

Classify elements based on electron configurations.

Distinguish representative elements and transition metals

Prior Knowledge

As we have learned when identifying mass, and atomic number, we will be looking at the periodic table and giving specific groupings to the elements we find.

Squares in the Periodic Table

The periodic table displays the symbols and names of the elements, along with information about the structure of their atoms.

The Groups

Group 1A- Alkali Metals, named because reaction with water forms alkalies (strong bases).

Group 2A Alkaline Earth Metals, named because they exist as strong bases, and still remain solid in high temperatures

Found in groups 17 or 7A, Halogens are named after the salts they form.

KEYWORDS- ALKALI METALS, ALKALINE EARTH METALS, HALOGENS

Electron Configurations in Groups

Elements can be sorted into 4 different groups based on their electron configurations: Noble Gases

Representative Elements

Transition Metals

Inner Transition Metals

Noble gases are the elements in group 8A, or 18. Also known as inert gases

Very Stable = Don’t React

Electron configurations have complete s and p sublevels.

KEYWORD- NOBLE GASES

Representative Elements are in Groups 1A through 7A Displays a wide range of properties

Contains metals, nonmetals, and metalloids

Outer s and p electron configurations are not filled

KEYWORD- REPRESENTATIVE ELEMENTS

Transition metals are in the “B” columns of the periodic table Electron configurations has outer s sublevel full, and is

entering the “d” orbital

A transition between the metal and nonmetal area

KEYWORD- TRANSITION METALS

Inner Transition Metals are located below the main body of the table, in two horizontal rows Electron configuration has the outer s sublevel full, and is

now filling the “f” sublevel

Formerly called “rare-earth” elements, but this is not true because some are very abundant

KEYWORD- Inner Transition Metals

6.3 Objectives

Describe trends among the elements for atomic size.

Explain how ions form.Describe periodic trends for

first ionization energy, ionic size, and electronegativity.

Prior Knowledge

We know we can organize the periodic table by properties and by atomic number.

These two concepts give rise to trends that we can follow across the periodic table.

Trends in Atomic Size

Atoms are too small, molecules give us clearer images.

We can find the atomic radius, half the distance between the nuclei of two atoms of the same element when joined.

Ions

An Ion, is a atom or group of atoms that has a positive or negative charge.

Equal protons and electrons = neutral

More protons = positive

More electrons = negative

Ions

Positive and negative ions form when electrons are transferred between atoms.

Typically electrons are lost from the valence level of one atom, and relocate onto the valence shell of another atom.

Valence Electrons

Valence Electrons are located in the outer most shell of an atom. And according to the electron configurations exist in the final sublevel.

Keyword- Valence Electrons

The charge of an ion also gives the atom a unique name.

A cation is any atom that has gained a positive charge, and lost an electron.

An anion is any atom that has gained a negative charge and gained an electron.

KEYWORDS- CATION, AND ANION

Does It Lose or Gain Electrons

One very important factor is for ions is knowing whether the atom would rather gain or lose an electron.

Luckily there is a pattern

Stability of the Noble Gases

The way we discover if an atom gains or loses electrons is based off the noble gases, and the group it is in.

We learned that Noble gases are very stable and un-reactive, so they have no need to gain or lose electrons.

The way we determine weather or not an electron is gained is by how close the atom is to the noble gases.

Trends in Ionization Energy

Ionization energy is the energy required to remove an electron from an atom.

Ionization energy tends to decrease from top to bottom within a group, and increase left to right across a period.

KEYWORD- IONIZATION ENERGY

Trends in Ionic Size

Cations are always smaller than their neutral parent.

Anions are always larger than their neutral parent.

Trends in Electronegativity

Electronegativity is the ability of an atom of an element to attract electrons when the atom is in a compound.

We assign elements a set of values from 0.7 to 4.0 which describe the tendency for that element to attract electrons.

KEYWORD- ELECTRONEGATIVITY