The Periodic Table

The periodic table is a chart that organizes the elements based on their atomic properties. Elements in the periodic table are organized according to the periodic law. The periodic law states that chemical and physical properties of elements are periodic functions of their atomic numbers (the number of protons in the nucleus). As the atomic number of elements increases, different elements display similar characteristics at regular intervals.

Periodic law states that elements are arranged _______________________________________________________________.

• in alphabetical order.

• from largest to smallest.

• as periodic functions of their atomic numbers.

• there is no rhyme or reason.

In 1869, Dmitri Mendeleev developed the first periodic table, organizing the elements according to atomic weight. When he ordered the elements, he noticed that there were patterns of repeating properties. The modern periodic table sequences elements from left to right by atomic number.

This was the first person to organize a periodic table.

• Neils Bohr

• Dmitri Mendeleev

• Democritus

• Ernest Rutherford

It stacks the elements in columns according to the number of valence electrons in an atom of the element. Valence electrons are those in the outermost shell of the atom and the ones that participate in reactions. The number of valence electrons is associated with the element’s reactivity. Elements with the same number of valence electrons behave in a similar way in reactions and so are grouped together in the same column on the periodic table.

What does the amount of valance electrons determine about an element?

• Its row in the table.

• Its atomic number.

• Its atomic mass.

• Its reactivity with other elements.

The maximum number of valence electrons an atom can have is eight, with the exception of helium, which can have only two. In each row, or period, of the periodic table, the last element on the right has the maximum number of valence electrons. Its outermost shell is full, and a new period in which the element on the far left has only one valence electron begins in the next row.

How do you determine how many valance electrons an element has?

• Count how far over it is from the left in its row.

• Count which row it is in.

• They all have eight.

• You can not determine this from the periodic table.

In the periodic table, similar elements are arranged in vertical columns called groups. Some of the major groups include Group 1: alkali metals; Group 2: alkaline earth metals; Group 17: halogens; and Group 18: noble gases. Elements within each group have similar properties and characteristic behaviors because of their similar numbers of valence electrons.

In what direction are groups arranged in the periodic table?

• Side to side

• Up and down.

• Diagonally

• In sections.

Alkali metals have 1 valence electron, making them highly reactive. With the exception of hydrogen, they tend to be very soft metals with low melting points. Examples include sodium and potassium.

Alkaline earth metals have 2 valence electrons and also are highly reactive and have high melting points. Examples include calcium and magnesium.

Halogens have 7 valence electrons and therefore are highly reactive. They tend to form compounds in nature. Examples include chlorine and fluorine.

Noble gases have a complete outer shell with 8 valence electrons, making them nonreactive. They are typically colorless, odorless gases. Examples include helium, neon, and argon.

Which group of elements tend to form compounds in nature?

• Alkaline metals

• Alkaline Earth metals

• Halogens

• Noble Gases

Alkali metals have 1 valence electron, making them highly reactive. With the exception of hydrogen, they tend to be very soft metals with low melting points. Examples include sodium and potassium.

Alkaline earth metals have 2 valence electrons and also are highly reactive and have high melting points. Examples include calcium and magnesium.

Halogens have 7 valence electrons and therefore are highly reactive. They tend to form compounds in nature. Examples include chlorine and fluorine.

Noble gases have a complete outer shell with 8 valence electrons, making them nonreactive. They are typically colorless, odorless gases. Examples include helium, neon, and argon.

Which group is highly reactive with high melting points?

• Alkaline metals

• Alkaline earth metals

• Halogens

• Noble gases

The periodic table is further arranged into three major regions, including the metals, metalloids, and non-metals. Metals are on the left of the table; they are shiny and flexible, conduct heat and electricity, and participate in ionic reactions. Non-metals are on the far right of the table; they are dull and brittle, are poor conductors, and typically participate in ionic reactions.

Which one is NOT a major region of elements in the periodic table?

• Metals

• Mettaloids

• Non metals

• Gases

Carbon and silicon, however, are examples of non-metals that participate in covalent reactions. Metalloids are located in a zig-zagging line between the two other regions. Metalloids are solid semi-conductors. In contrast to metals and non-metals, metalloids participate in covalent reactions.

Where would you look on the table to find the mettaloids?

• In a zigzag line on the right.

• In column 17

• On the bottom

• On the top

The elements in groups 3-12 are called the transition metals. These are similar to the metals in that they are flexible and good conductors but different in that they have unique valence electron structure. They typically form coordinate complexes in which one atom is surrounded by several more in a large complex. Iron, gold, and copper are examples of transition metals.

Which group are the transition metals most like?

• Metals, they are flexible and good conductors.

• Non metals, they a unique valence electron structure.

• Noble gases, they don't want to bond with anything else.

• They are like both metals and non metals in some ways.