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Unit 5 Section 2 Notes A Guided Tour of the Periodic Table
Who is Dmitri Mendeleev? (1834-1907) 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.
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) 65-30 = 35 neutrons