The Nature of Matter K 1.2 The Simplest Matter

The Simplest Matter An element is matter made of only one kind of atom. At least 118 elements are known and about 90 of them occur naturally on Earth. The other elements are known as synthetic elements. The elements are organized on the periodic table by their properties.

The Simplest Matter The rows in the table are called periods. The elements in a row have the same number of energy levels. The columns are called groups. The elements in each group have similar properties related to their structure.

The Simplest Matter The top number is the element's atomic number. It tells you the number of protons in the nucleus of each atom of that element. Isotopes (I suh tohps) are atoms of the same element that have different numbers of neutrons. An atom's mass number is the number of protons plus the number of neutrons it contains. The atomic mass is the weighted average mass of the isotopes of an element.

The Simplest Matter Metals generally have a shiny or metallic luster and are good conductors of heat and electricity. All metals, except mercury, are solids at room temperature. Metals are malleable which means they can be bent and pounded into various shapes. Metals are also ductile, which means they can be drawn into wires without breaking.

Nickel - Ni Gold - Au Mercury - Hg

The Simplest Matter Nonmetals are elements that are usually dull in appearance. Most are poor conductors of heat and electricity. Metalloids are elements that have characteristics of metals and nonmetals. Some metalloids are shiny and many are conductors.

Silicon - Si Carbon - C Helium - He