Unit 5 Section 2 Notes A Guided Tour of the Periodic Table

Who is Dmitri Mendeleev? ( )  In 1869, Dmitri Ivanovitch Mendeléev created the first accepted version of the periodic table.

What is the Periodic Table?  Shows all known elements in the universe  Organizes elements by chemical properties

The Periodic Table  The periodic table groups similar elements together. This organization makes it easier to predict the properties of an element based on where it is in the periodic table.

Elements  Elements in the periodic table are represented by their symbols. The first letter is ALWAYS capital If there is a second letter, it is ALWAYS lowercase  Every element has its own unique symbol C Carbon Cu Copper

How is the Periodic Table Organized?  The elements are arranged based on the number of protons in the nucleus.  Periodic Law: states that when elements are arranged in order of increasing atomic number, similarities in their properties will occur in a regular pattern.

Periods in the Periodic Table  Period: a horizontal row of elements in the periodic table  As you move from left to right in a period, the number of protons and electrons increases by one  Elements in the same period DO NOT have similar properties; in fact, they change greatly across the row  The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas.

Groups or Families in the Periodic Table  Group or family: a vertical column of elements in the periodic table  All elements in a family have the same number of valence electrons, so they have similar properties For example, lithium (Li), sodium (Na), potassium (K), and other members of group 1 are all soft, white, shiny metals. These elements are NOT exactly alike because they have different numbers of protons

Ions  Ionization: the process of adding electrons to or removing electrons from an atom  Ion: an atom that has lost or gained one or more electrons and has a net electric charge  Cation: an ion with a positive charge  Anion: an ion with a negative charge

Goal of Atoms  All atoms want to have a FULL octet (8 e - in outer shell) They do this by gaining, losing, or sharing electrons

Metals and Electrons  Metals LOSE electrons to form cations  Example: Lithium loses one electron to become a lithium ion, written as Li + 3 p + 4 n 0 Second energy level can hold up to 8 e-. It is easier to lose 1 e- than gain 7 more. 3 p + 4 n 0 3 electrons 2 electrons After lithium loses an electron, it has a full outermost energy level.

Nonmetals and Electrons  Nonmetals GAIN electrons to form anions  Example: Fluorine gains one electron to become a fluoride ion, written as F - 9 p + 10 n 0 9 p + 10 n 0 9 electrons10 electrons Second energy level can hold up to 8 e-. It is easier to gain 1 e- than lose 7 more. After fluorine gains an electron, it has a full outermost energy level.

So, how do compounds form?

Atomic Number  Atomic Number: how many protons are in the nucleus of an atom  Remember that ATOMS are neutral, so they have equal numbers of protons and electrons Therefore, atomic number also tells the number of electrons for atoms only

Mass Number (Atomic Mass)  Mass Number: the number of protons and neutrons in an atom Mass number is ONLY protons and neutrons because they provide most of an atoms mass  The same element can have different mass numbers because they may have different numbers of neutrons.

Isotopes  Isotopes: atoms of the same element having the same number of protons but different numbers of neutrons Each “version” of the atom has the same number of protons and electrons

Isotopes  Some isotopes are more common than others  For example, protium is found most often

Calculating Neutrons in an atom  To calculate the number of neutrons in an atom, take mass number minus atomic number. Mass Number - Atomic Number # of Neutrons

Average Atomic Mass  In the periodic table, the atomic mass is a decimal because it is an average of all the naturally occurring isotopes  When calculating neutrons from average atomic mass, round to the nearest whole number  Example: How many neutrons are in Zinc? (Atomic Number 30; Average atomic mass 65.39) = 35 neutrons

How do you read the Periodic Table?

Periodic Table Song  WtFtEM WtFtEM