Learning Targets

In 1860 chemists met at the First International Congress of Chemists in Germany. They established a uniform method of measuring the atomic mass of each element. Once they were all using the same units and techniques, the race began for making a connection between the atomic mass of an element and its other properties. Mendeleev tried to create a chart of the elements for a text book he was writing.

Mendeleev noticed that when the elements were arranged in order of increasing atomic mass, certain similarities in their chemical properties appeared at regular intervals. This repeating pattern is known as periodic law.

Mendeleev’s table had elements in order of atomic mass and in each column the elements had similar properties. He was the only person to leave empty spaces on his table for elements that hadn’t been discovered yet. He predicted the physical and chemical properties of these elements correctly!! He also switched the order of some elements (like Te and I) so that they fit in the correct families. Later, Moseley discovered atomic number and the table was put in order of the number of protons instead of the mass.

Elements on the periodic table now go in order of atomic number. As you move across a period, (a horizontal row of the table) the atomic number increases by one. As you move down a group, (a vertical column on a periodic table) the properties of the elements are similar Why? Elements in the same column have the same amount of valance electrons!

You are required to know the properties and locations of the following groups: Noble gases Lanthanides Actinides Alkali Metals Alkaline Earth Metals Transition metals Halogens Main Group Elements

Metals are found to the left of the jagged red line. Non-metals are found to the right of the jagged red line. MetalsNonmetals Good conductors of heat and electricity Poor Conductors of heat and electricity ShinyDull DuctileNon-ductile MalleableBrittle Corrodes in water Usually Solid (Except Hg)Mostly Gases

Metalloids (metal-like) have properties of both metals and non-metals. They are solids that can be shiny or dull. They conduct heat and electricity better than non-metals but not as well as metals. They are ductile and malleable. Include: B, Si, Ge, As, Sb and Te.

An incomplete valence electron level. All atoms (except hydrogen) want to have 8 electrons in their very outermost energy level (This is called the rule of octet.) Atoms bond until this level is complete. Atoms with few valence electrons lose them during bonding. Atoms with 5, 6, or 7 valence electrons gain electrons during bonding.

These were not included in Mendeleev’s table because they hadn’t been discovered yet. They were hard to discover because they are completely unreactive. They are colorless gases that are hard to detect. They are inactive or inert because their outermost energy level is full. All the noble gases are found in small amounts in the earth's atmosphere. They are in column 18 or 8A

These are also known as the rare earth elements. They are the f- block of the periodic table. Many of the lanthanides are very similar in properties so it was very difficult for chemists to differentiate between them. All of the actinides are radioactive. The majority of actinides are not found in nature and have been synthesized by humans. They have been taken out of their correct place to save space.

Everything in column 1A except hydrogen! Each has one electron in its outermost “s” sublevel. Silvery white metals that are soft. Extremely reactive because they only have one valance electron which they can get rid of easily. They are not found in nature as pure substances because they readily react when they come in contact with other substances. Relatively low melting points.

All elements in column 2A. Each has two electrons in the outermost “s” sublevel. They are very reactive as well but not as reactive as the alkali metals. These metals are harder, denser and stronger than alkali metals. They also have higher melting points. They are also not found in nature as pure element.

Transition Elements include all elements in the d block. These are the metals you are probably most familiar with: copper, tin, zinc, iron, nickel, gold, and silver. They are good conductors of heat and electricity and are typically shiny. Some transition metals do not follow the electron configuration patterns: Platinum is {Xe}6s 1 4f 14 5d 9 They are less reactive than alkali and alkaline earth metals.

All the elements in group 17 or 7A Halogens have 7 valence electrons, which explains why they are the most reactive non-metals. They only have to gain 1 electron in order to have a valance number of 8. This can happen quickly! They especially like to react with metals to form compounds called salts They are never found free in nature.

All the elements in the s and p blocks. Or all of the “A” column elements. As you move across the periodic table each one has one more valance electron than the main block element before it. Columns 1A, 2A and 3A are likely to lose electrons to have a 8 valance electrons. Columns 5A, 6A, and 7A are likely to gain electrons to have a 8 valance electrons. Elements in column 4A will gain or lose electrons to have 8 valance electrons.