Make sure you know…

REMEMBER THAT THE MASS WILL ALWAYS BE THE BIGGER OF THE TWO NUMBERS One 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

Below is a model of a carbon atom REMEMBER THAT THE MASS WILL ALWAYS BE THE BIGGER OF THE TWO NUMBERS 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. Below is a model of a carbon atom

REMEMBER THAT THE MASS WILL ALWAYS BE THE BIGGER OF THE TWO NUMBERS 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. REMEMBER THAT THE MASS WILL ALWAYS BE THE BIGGER OF THE TWO NUMBERS

THE PERIODIC TABLE OF ELEMENTS Groups and Families

Content Limits Students will NOT: Students will:  determine an element's number of valence electrons  explain how chemical and physical properties depend on its valence grouping  predict ionic bonding pairs  identify molecules which are covalently bonded using valence electrons  require memorization of the periodic table  require memorization of orbital configuration  assess VESPR structures  assess electron configurations

https://www.youtube.com/watch?v=VgVQKCcfwnU

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

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 Horizontal rows are called PERIODS

All of the elements in the same group have similar PROPERTIES. The Periodic Table E.g. consider the group 1 metals. They all: Are soft Can be easily cut with a knife React with water

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

The Periodic Law - Periods Each row in the table of elements is a period. Hydrogen, the first element in Period 1, has one electron in its first energy level. Lithium, the first element in Period 2, has one electron in its second energy level. Sodium, the first element in Period 3, has one electron in its third energy level. This pattern applies to all the elements in the first column on the table.

The Periodic Law - Groups Each column in the periodic table is called a group. The elements in a group have similar electron configurations, so members of a group in the periodic table have similar chemical properties. This pattern of repeating properties is the PERIODIC LAW.

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. Properties vary across a period because the number of valence electrons increases from left to right.

Elements in a group have similar properties They have the same number of valence electrons. However, the properties are not identical because the valence electrons are in different energy levels. Because hydrogen has a single valence electron, it is grouped with other elements, such as lithium, that have only one valence electron.

Classifying Elements in the Periodic Table

What categories are used to classify elements on the periodic table? Elements are classified as metals, nonmetals, and metalloids. The periodic table presents three different ways to classify elements. State: solid, liquid, or gas Occurrence in nature: elements that do not occur naturally General properties:, nonmetal, or metalloid

Metals 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. 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.

Nonmetals Nonmetals generally have properties opposite to those of metals. Nonmetals are elements that are poor conductors of heat and electric current. Nonmetals have low boiling points – many nonmetals are gases at room temperature. Nonmetals that are solids at room temperature tend to be brittle. If they are hit with a hammer, they shatter or crumble.

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. For example, a metalloid’s ability to conduct electric current varies with temperature. Silicon (Si) and germanium (Ge) are good insulators at low temperatures and good conductors at high temperatures.

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 Shells or energy levels The “s" shell is the one closest to the nucleus, and “f" is the farthest away. Atoms in the same column (group) in the periodic table have the same number of valence electrons. You will use the lowercase letters s, p, d, and f, for the sub-orbitals. 

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. When the second energy level has 8 electrons, the next electrons go into the third energy level until the third level has 8 electrons and 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, least reactive, when their outermost electron shell is full. Most atoms want 8 electrons in their outer shell. Atoms want a full outer shell of electrons, so the lose, gain, or share electrons with other elements, forming compounds, until they have 8 valence electrons and become stable.

Valence electrons and the periodic table The general trend is for an atom to gain or lose electrons, either directly (leading to formation of ions) or by sharing electrons with other atoms so as to become stable. The elements in Groups 1, 2 and 13 tend to give up their valence electrons to form positive ions such as Na+, Mg2+ and Al3+, as well as compounds NaH, MgH2 and AlH3. Elements in Groups 15-17 tend to acquire electrons, forming ions such as P3–, S2– and Cl– or compounds such as PH3, H2S and HCl. The Group 14 elements do not normally form ions at all, but share electrons with other elements in compounds such as CH4.

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.