ATOMS AND THE PERIODIC TABLE

Chapter 3

Atom Review (Dalton’s Atomic Theory) Atom: the smallest particle that still has

the properties of an element

Elements are made of atoms and atoms of the same element are alike

Atoms combine in order to make molecules (either elements or compounds)

Structure of the Atom

A. Inside the nucleusProtons (positive charge)Neutrons (no charge)

B. Outside the Nucleus Electrons (negative charge) Electrons are orbiting the nucleus so fast

that we can’t determine their exact position

C. Neutral atoms have no overall charge They have equal numbers of protons and

electrons

Calculating Protons, Neutrons, and Electrons # of protons: Always the same as the

atomic # on the periodic table

#of electrons: usually the same as the atomic number. (different in atoms that have a charge)

# of neutrons: Atomic mass – atomic #

Ex. Chlorine has 18 neutrons

Drawing Electrons in their orbitals (shells) The first orbital can hold 2 e- The second orbital can hold 8 e- The third energy level can hold 8 e- Valence Electrons: the electrons in an

atom’s outermost shell

Example:

Changing Atoms

A. Ions- Atoms that carry a charge Atoms gain/lose electrons from their

valence shell in order to be more stable. This causes the # of protons to no longer

equal the # of electrons.

B. Two types of Ions Anions- Negatively charged atom

(gained e- , Has more e- than p+) Cations- positively charged atom

(lost e-, has less e- than p+)

Changing atoms (cont.)

Isotopes- Atoms that have the same number of protons, but different numbers of neutronsA. Changes the atomic mass of the atom

B. The atomic mass written on the periodic table is the weighted average atomic mass of ALL the isotopes.

Changing the # of protons = New Element

Developed by a Russian chemist named Dmitri Mendeleev (duh-MEE-tree mehn-duh-LAY-uhf) Mendeleev used the following categories to

organize his table: chemical properties physical properties atomic mass density color melting point Valence electrons

Developed by a Russian chemist named Dmitri Mendeleev (duh-MEE-tree mehn-duh-LAY-uhf)

Design of the Periodic Table organizes information in a logical,

usable, and meaningful way allows prediction of physical and

chemical properties of an element by position

can predict how elements will react with other elements

arranged in columns and rows because of similar characteristics

Columns in the Periodic Table

vertical classification or groupings

often referred to as families or groups

elements within the same family have similar properties

Rows in the Periodic Table

horizontal classification or groupings each row is called a period elements in a period are not alike in

properties, properties change greatly across a given row

the first element in a period is a very reactive metal

the last element in most periods is a noble gas

only seven periods

Physical and Chemical Properties of Metals Physical Properties luster (shininess) conductivity of

heat and electricity high density high melting point ductility (they are

ductile) malleability (they

are malleable)

Chemical Properties

Tend to lose their electrons in a reaction

Metals will have either 1, 2, 3, or 4 electrons in their outermost energy level (depending on the family)

Alkali Metals Group 1 Very reactive because

they only have one valence electron

Forms a 1+ ion (ex. Na+) Found in nature as a

compound http://www.youtube.com/wat

ch?v=m55kgyApYrY YouTube - Alkali Metals: Expl

osive reactions

Alkaline Earth Metals Group 2 2 valence electrons Form 2+ Ions (ex.

Ca2+) Reactive, but less

reactive than alkali metals

Transition Metals Groups 3-12 Typically have 3

valence electrons Less reactive than

first 2 families Most metals we

think of are from this family

Very good conductors of heat and electricity

Nonmetals (right side of PT) Physical

Properties No luster Don’t conduct heat

or electricity well Not malleable or

ductile Can be solids,

liquids, or gases

Chemical Properties

Typically gain electrons to fill valence shell

Form Negative Ions (ex. O2-)

React mainly with metals

Halogens Group 17 Have 7 valence

electrons Very reactive

nonmetals because they need one electron for full valence shell

Are found as solids, liquids and gases at room temp

Noble Gases Group 18 Have 8 valence

electrons (He only has 2)

Full valence shell makes them unreactive

Also called “inert”

Metalloids (Semi-conductors) Only 7 elements

(B, Si, Ge, As, Sb, Te, Po)

Classified as nonmetals but have some properties of metals

Can conduct heat and electricity but not as well as metals.