GET ORGANIZED The Periodic Table of Elements

The Periodic Table of Elements Mendeleev set up the periodic table of elements from left to right, top to bottom in order of increasing atomic number

REMEMBER THAT THE MASS WILL ALWAYS BE THE BIGGER OF THE TWO NUMBERS On the periodic table you will find four pieces of information for each element – Atomic Mass Atomic number Element symbol Element name REMEMBER THAT THE MASS WILL ALWAYS BE THE BIGGER OF THE TWO NUMBERS

Element Symbols Mg = Magnesium First letter of a chemical symbol will ALWAYS be capitalized. Second letter will ALWAYS be lower case

WHAT DOES IT ALL MEAN? Atomic Number = # of Protons # of Protons = # of electrons in a neutral atom Atomic Mass = # of protons + # of neutrons Protons identifies the element, its electrical structure and its chemical and physical properties. Isotopes are the same element with different # of neutrons. That is why you will see more than one mass number sometimes.

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Horizontal rows are called PERIODS Periodic table Mendeleev The periodic table arranges all the elements in groups according to their properties. Vertical columns are called FAMILIES or GROUPS 4A stopped Here Horizontal rows are called PERIODS

All of the elements in the same group have similar PROPERTIES. The Periodic Table

Elements in the same group have the same number of electrons in the outer shell (this correspond to their group number) These elements have 3 electrons in their outer shells These elements have 7 electrons in their outer shell E.g. all group 1 metals have 1 electron in their outer shell

Why do the elements in a group have similar properties? Elements in a group have similar properties because they have the same number of valence electrons. A valence electron is an electron that is in the highest occupied energy level of an atom. When the groups in the periodic table are numbered from 1 through 8, the group number matches the number of valence electrons in the electron configuration of an element in that group. Valence electrons play a key role in chemical reactions.

What categories are used to classify elements on the periodic table? Elements are classified as metals, nonmetals, and metalloids or transition metals.

Metals Except for mercury, metals are solids at room temperature. Most metals are malleable. Many metals are ductile; that is, they can be drawn into thin wires. The majority of the elements on the periodic table are classified as metals. Metals are elements that are good conductors of electric current and heat.

Metalloids Metalloid elements are located on the periodic table between metals and nonmetals. Metalloids are elements with properties that fall between those of metals and nonmetals.

Nonmetals Nonmetals generally have properties opposite to those of metals. Nonmetals are elements that are poor conductors of heat and electric current and have low boiling points

The Noble Gases The elements in Group 8A are called noble gases. Helium has two valence electrons. Each of the other noble gases has eight valence electrons. That means they never need to form bonds with other elements because they are stable alone.

Energy levels

Filling the energy levels The number of electrons is equal to the number of protons which gives us the atomic number. Because of this, each element has a different number of electrons and thus fills the energy levels at different points

Electron Cloud or energy levels The first energy level can accept up to 2 electrons The second and third energy levels hold up to 8 electrons each The fourth and fifth energy levels hold up to 18 electrons each.

The red dots represent electrons in different energy levels Each energy level can only “hold” a certain number of electrons. When the first energy level has 2 electrons, the next electrons go into the second energy level until the second level has 8 electrons, the next electrons go into the third energy level so on… The electrons in the energy level farthest from the nucleus are called valence electrons.

Let’s tie it together… Atoms are most stable and least reactive, when their outer shell is full. Most atoms want 8 electrons in their outer shell. Atoms will lose, gain, or share electrons with other elements until they have 8 valence electrons and become stable.