4.4 Groups of Elements The periodic table groups elements with similar properties. You can quickly identify an element as a metal if it is on the left or in the centre of the table. Non-metals are generally found on the right side.

Chemical Groups The set of elements in the same column in the table is called a chemical group (having similar chemical and physical properties). These properties, however, vary from element to element in a column.

Periods The horizontal rows of elements are called periods. The first period contains two elements: hydrogen and helium. As you go from left to right within a row, the atomic number increases and the elements gradually change from metallic (lithium) to non-metallic (flourine), and then finally to noble gases (neon) at the far right.

Assignment Use the colour code (in the following notes) and colour the following sections on your periodic table: Noble gases Alkali Metals Halogens Group of One Metalloids Metals

Group of One Hydrogen is a unique element (yellow). It’s most common isotope has only a single proton and no neutron in its nucleus. Hydrogen doesn’t have much in common with the alkali metals. It’s a colourless, odourless, tasteless, highly flammable gas. Almost all of Earth’s hydrogen exists in combination with other elements. Its reactivity is too great for it to exist in the atmosphere as a free element.

Alkali Metals Occupy the far left column of the periodic table (green). Extremely reactive. Found in nature only as compounds, and are found everywhere on Earth. Most common are sodium compounds, which occur in plants, animals, soil and sea water. Lithium, sodium, potassium, etc…shiny, silvery.

Metalloids Elements that possess both metallic and non-metallic properties. Found on both sides of the zigzag line that divides the metals from the non-metals. (purple) Ex. silicon, boron, germanium, arsenic, antimony, tellurium, and polonium

Halogens Occupy the 17th column of the periodic table (fluorine, chlorine, bromine…) Most reactive non-metals. (red) Because of their reactivity, they almost always appear naturally as compounds, not as elements. Most common halogen compounds are chlorine compounds found in living things, ocean water and rocks.

Noble Gases Occupy the far right column of the periodic table (blue). All gases at room temperature, the noble gases are often called inert gases because they are so unreactive, almost never forming chemical compounds with other elements. Argon makes up 1% of every breath you inhale. Very useful elements. Ex.: neon, helium

Metals If you look at what’s not coloured on your periodic table, all of those elements (left of metalloids) are metals. Lightly shade the metals in orange.

Questions Questions 1, 3, 4, and 5 page 113