Periodic Table of Elements Notes Table of Contents Periodic Table of Elements Notes The Simplest Matter

The Elements—One Kind of Atom The Simplest Matter 2 The Elements—One Kind of Atom An element is matter made of only one kind of atom. At least 115 elements are known and about 90 of them occur naturally on Earth.

The Elements—One Kind of Atom The Simplest Matter 2 The Elements—One Kind of Atom Examples of naturally occurring elements include the oxygen and nitrogen in the air you breathe. The other elements are known as synthetic elements.

The Periodic Table— Charting the Elements The Simplest Matter 2 The Periodic Table— Charting the Elements Chemists have created a chart called the periodic table of the elements to help them organize and display the elements. Each element is represented by a chemical symbol that contains one to three letters.

The Simplest Matter 2 The Periodic Table

The Periodic Table— Charting the Elements The Simplest Matter 2 The Periodic Table— Charting the Elements The elements are organized on the periodic table by their properties. 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.

Identifying Characteristics The Simplest Matter 2 Identifying Characteristics Each element is different and has unique properties. These differences can be described in part by looking at the relationships between the atomic particles in each element.

Number of Protons and Neutrons The Simplest Matter 2 Number of Protons and Neutrons 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. Every atom of chlorine, for example, has 17 protons in its nucleus.

The Simplest Matter 2 Isotopes The number of protons changes from element to element, every atom of the same element has the same number of protons. However, the number of neutrons can vary even for one element. Isotopes (I suh tohps) are atoms of the same element that have different numbers of neutrons.

The Simplest Matter 2 Isotopes You can tell someone exactly which isotope you are referring to by using its mass number. An atom's mass number is the number of protons plus the number of neutrons it contains.

The Simplest Matter 2 Isotopes Hydrogen has three isotopes with mass numbers of 1, 2, and 3. (Draw the picture)

The Simplest Matter 2 Atomic Mass The atomic mass is the weighted average mass of the isotopes of an element. The atomic mass is the number found below the element symbol. The unit that scientists use for atomic mass is called the atomic mass unit, which is given the symbol u. It is defined as 1/12 the mass of a carbon-12 atom.

Classification of Elements The Simplest Matter 2 Classification of Elements Elements fall into three general categories—metals, metalloids (ME thu loydz), and nonmetals. 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.

Classification of Elements The Simplest Matter 2 Classification of Elements 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.

The Simplest Matter 2 Other Elements Nonmetals are elements that are usually dull in appearance. Most are poor conductors of heat and electricity. The nonmetals are essential to the chemicals of life.

The Simplest Matter 2 Other Elements Metalloids are elements that have characteristics of metals and nonmetals. All metalloids are solids at room temperature. Some metalloids are shiny and many are conductors.

Question 1 2 An element is matter made of only _______ kind of atom. Section Check 2 Question 1 An element is matter made of only _______ kind of atom. A. one B. two C. three D. four NC: 4.03

Section Check 2 Question 2 Chemists organize all the known elements on a particular chart known as the _______. NC: 4.03

Section Check 2 Question 3 Chlorine-35 has 18 neutrons in its nucleus, while chlorine-37 has 20. How can these both be chlorine atoms? NC: 4.03

Section Check 2 Question 1 Answer The answer is A. Aluminum is an example of an element. NC: 4.03

Section Check 2 Question 2 Answer It is called the periodic table of the elements. Not only does the periodic table organize the known elements, it helps predict properties of those that have yet to be discovered. NC: 4.03

Section Check 2 Question 3 Answer Chlorine-35 and chlorine-37 are isotopes. Atoms of the same element can have different numbers of neutrons, as long as they have the same number of protons. NC: 4.03