Unit 5 Section 2 Unit 5 Section 2 NotesNotes

A Guided Tour of the Periodic A Guided Tour of the Periodic TableTable

Who is Dmitri Mendeleev? Who is Dmitri Mendeleev? (1834-1907)(1834-1907) In 1869, Dmitri Ivanovitch Mendeléev

created the first accepted version of the periodic table.

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

properties

The Periodic TableThe 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.

ElementsElements 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

CCarbon

Cu

Copper

How is the Periodic Table How is the Periodic Table Organized?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 Periods in the Periodic TableTable 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 Groups or Families in the Periodic TablePeriodic 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

IonsIons 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 n0

Second energy level can hold up to 8 e-. It is easier to lose 1 e- than gain 7 more.

3 p+

4 n0

3 electrons2 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 n0

9 p+

10 n0

9 electrons 10 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 So, how do compounds form?form?

So, how do compounds So, how do compounds form?form?

So, how do compounds So, how do compounds form?form?

Atomic NumberAtomic 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 Number (Atomic Mass)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.

IsotopesIsotopes 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

IsotopesIsotopes Some isotopes are more common than

others For example, protium is found most often

Calculating Neutrons in an Calculating Neutrons in an atomatom To calculate the number of neutrons in an

atom, take mass number minus atomic number.

Mass Number

- Atomic Number

# of Neutrons

Average Atomic MassAverage 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

How do you read the Periodic How do you read the Periodic Table?Table?

Periodic Table Song http://www.youtube.com/watch?v=zUDDi

WtFtEM