The Periodic Table Help (page 2)
Periods And Groups
Like a family history, the elements are arranged in family groups such as noble gas, halogen, metal, rare earth, transitional metal, non-metal, alkali metal, and alkaline earth. Just as genetic analysis helps biologists and physicians to determine a person’s make-up, so the grouping of elements into families and groups helps chemists to understand similar properties of different elements.
Elements with similar boiling or melting points usually act the same way when exposed to the same experimental conditions. The same is true of freezing and vaporization points.
The Periodic Table is the most important tool in general chemistry. Probably only the Bunsen burner (laboratory gas flame) rivals it in a distant second place. The amount of information pulled together in one place makes calculations, reactions, and the study of matter a whole lot easier to decipher.
Basically, the Periodic Table is divided into rows and columns, known as periods and groups . Dividing elements into periods and groups helps classify them by their specific characteristics.
Each period ends with an element known as a noble gas. Like kings and queens set apart in impenetrable castles, these gases are chemically unreactive and composed of individual atoms.
A period contains the elements in one horizontal row of the Periodic Table.
The first period contains only hydrogen (H) and helium (He). The second period has 8 elements: lithium (Li) through neon (Ne). The third period also contains 8 elements: sodium (Na) through argon (Ar). The fourth period has 18 elements: potassium (K) through krypton (Kr). The fifth period also has 18 elements: rubidium (Rb) through xenon (Xe). The sixth period has 32 elements; cesium (Cs) through radon (Rn). To make the table less bulky, the sixth and seventh period rows have been divided between 57, 58 and 89, and 90. These rows are shown fully expanded at the bottom of the chart. The seventh period is not complete, but includes gaps just as Meyer did earlier to allow for additional elements: francium (Fr) through lawrencium (Lr). Placeholders are in debate through element 118 and sometimes are not included on older Periodic Tables.
The groups of the Periodic Table are numbered most frequently with Roman numerals. The International Union of Pure and Applied Chemistry (IUPAC), in order to avoid confusion, set up a standard numbering plan in which columns were numbered I-VIII, according to their characteristics.
A group contains the elements in one column of the Periodic Table.
These groups are further divided into A and B sub-groups with the A groups called the main groups or representative elements and the B groups called the transition elements. Numbers 58 (cerium) to 71 (lutetium) are known as the lanthanide series and 90 (thorium) to 118+ (ununoctium) as the actinide series of elements.
The Periodic Table divided into periods and groups is shown in Figure 4.4 .
As Meyer reported in his research, some elements with similar properties can be grouped together. Basically, groups of elements are divided into four main classes.
(1) Representative elements (groups IA-VIIA)
(2) Noble or inert gases (group VIII)
(3) Transition metals (group B elements)
(4) Inner transition metals
The representative elements or main group of elements is further defined. Group IA, the alkali metals (e.g., lithium, potassium), are all soft metals (except hydrogen, a gas) that react readily with water. Group IIA, known as the alkaline earth metals (e.g., beryllium, cadmium), are also reactive chemically. The halogens , in group VIIA, are all non-metals. Chalcogens , group VIA (e.g., oxygen, sulfur), comes from the Greek word chalkos meaning ore. Many ores are made with varying amounts of oxygen and sulfur. The remainder of the representative element groups (IIIA-VA) have not been given descriptive names.
The noble or inert gases (group VIII) are called inert since they seldom form chemical compounds. In fact, helium, neon, and argon refuse to play with anyone and don’t form any compounds at all. All these gases exist naturally as individual atoms in the environment.
The transition metals (group B) contain the more recognizable metals. They are used in construction, coins, and jewelry. The transition metals group includes iron, nickel, and chromium as well as gold, silver, and copper.
The inner transition metals consist of the 15 rare earth metals or lanthanides. They are all silvery white in color and used in such products as permanent magnets and headphones. The other inner transition metals, a set of elements named after the element actinium, include uranium, americium, and neptunium. They are primarily human-made elements. These metals are radioactive and used in advanced smoke detectors, neutron-detection devices and in nuclear reactions.
Metals Vs. Non-metals
It is important to observe that metals and non-metals are shown on the Periodic Table by a heavy zigzag line with metals to the left side and non-metals to the right. Figure 4.5 shows this dividing line.
Most metals are shiny and good conductors of heat and electricity.
Metals , about 80% of the elements, can be pulled into thin wires (ductile) or pounded into sheets (malleable). Mercury is the only metallic element that is liquid at room temperature.
Non-metals are basically everything else. Most are gases such as helium and argon, or brittle solids such as phosphorus and selenium. Bromine is the only liquid, non-metallic element at room temperature.
The elements found along the borderline of metals and non-metals are known as semi-metals or metalloids since they have the characteristics of both metals and non-metals. For example, silicon is used to make lubricants, computer circuits, and medical implants and joints.
If asked to learn only one thing in all of chemistry, pick the Periodic Table. Learn it and all the rest will fall into place.
Practice problems for these concepts can be found at - The Periodic Table Practice Test
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