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 itsown unique symbol Cu C Carbon 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
3 p+ 4 n0 3 p+ 4 n0 Metals and Electrons • Metals LOSE electrons to form cations • Example: Lithium loses one electron to become a lithium ion, written as Li+ Second energy level can hold up to 8 e-. It is easier to lose 1 e- than gain 7 more. After lithium loses an electron, it has a full outermost energy level. 2 electrons 3 electrons
9 p+ 10 n0 9 p+ 10 n0 Nonmetals and Electrons • Nonmetals GAIN electrons to form anions • Example: Fluorine gains one electron to become a fluoride ion, written as F- 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. 9 electrons 10 electrons
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
Periodic Table Song • http://www.youtube.com/watch?v=zUDDiWtFtEM