The Periodic Table

Dmitri Mendeleev(1834 – 1907)

•He organized elements into the first periodic table

•He arranged elements by increasing atomic mass

Henry Moseley(1913)

•He arranged elements according to atomic number rather than atomic mass

•The modern periodic table is arranged by atomic number

Periodic Law

The periodic law states that

there is periodic repetition of chemical and physical properties of elements

The Modern Periodic Table

There are 18 groups (columns up and down)

The group A’s (the tall columns) are called representative elements

•The group B’s (the middle columns) are called transition metals

There are seven periods(rows across the periodictable)

Metals are to the LEFT of the zig-zag line (except hydrogen!)

Metals in yellow

Nonmetals are to the RIGHT of the zig-zag line

nonmetals in red

Metalloids

•Metalloids are those elements ON the zig-zag line

Metalloids border the zig-zag line

Now . . .YOU fill in the chart using your book!

Metals

•solid at room temperature

•shiny (have luster) and smooth

•good conductors of heat and electricity

Metals

•malleable – “bendable” (can be pounded into sheets)

•ductile - can be pulled into wires

Metals

•react with acids

•mercury (Hg) is the only LIQUID metal

Nonmetals

•generally gases or brittle, dull looking solids at room temperature

•poor conductors of heat and electricity

•Bromine (Br) is the only LIQUID nonmetal

Metalloids

•sometimes called semimetals

•metalloids have properties of both metals and nonmetals

Metalloids

•silicon and germanium are two of the most important metalloids (they’re used in computer chips and solar cells)

Trends of the Periodic Table

Periodic LawIf elements are organized according to atomic number, their properties will repeat periodically

Four Periodic Trends:

1.Atomic radii

2.Ionic radii

3.Electronegativity

4.Ionization energy

Atomic RadiusThe atomic radius basically tells you the size of the atom. It is half the distance between two nuclei of identical atoms bonded together.

radius

The trend: atomic radii DECREASE across a

period•Why?

•Each time a positive proton is added to the nucleus, the negative electrons feel a greater attraction to the positively-charged nucleus and get “pulled in” tighter

Decreasing – getting smaller!

Trend: atomic radiiINCREASE down a group

•Why?

•electrons are added to higher and higher energy levels as you go down

Atomic radii DECREASE down a group!

The farther the electrons from the nucleus, the larger

the atomic radii!!!!!

Try these . . .

1.Which element has the larger atomic radius: C or F?

carbon

2.Which element has the smaller atomic radius: Ar or Kr?

argon

Ionic Radii

•Is basically the size of an ion or half the distance between the nuclei of two ions bonded together

What is ion???

Ionic Radii

•Ion – an atom with a charge (+ or - )

•An ion is formed when atoms lose or gain electrons

•What happens to an atom if it LOSES an electron?

it loses a negative charge so it becomes POSITIVE

Na +1

•A positively charged ion is called a cation

Na +1

Positive ions (cations) are smaller than the atoms they come from because they lose electrons making the atom smaller.

Na Na +1

•What happens to an atom if it GAINS an electron? It gets more negative

(so it has a negative charge) Cl -1

A negatively charged ion is

called an anion.

Cl -1

Negative ions (anions) are LARGER than the atoms they come from because they gain electrons – making the atom LARGER!

Cl -1 Cl

The trend:

•See the board

Remember . . .

•all atoms want a full octet (8 valence electrons)

•atoms with 1 valence electron will give up that electron VERY QUICKLY to become stable

example: •sodium has one valence electron: 1s22s22p63s1 •if sodium gives it away, then the configuration will be:

1s22s22p6

•sodium will have a full octet

•atoms with 7 valence electrons will hold on to those electrons VERY TIGHTLY

•they try to get one more and become stable

Ionization Energy•The amount of energy needed to remove an electron

•think of it as: how tightly an atom holds on to its electrons

The trend:•ionization energy INCREASES across a period

•Why?

•the more valence electrons an element has, the more difficult it is to remove them!

The trend:•Ionization energy DECREASES down a group

•Valence electrons in higher energy levels are NOT held as tightly because they are farther from the nucleus

•Therefore, it is easier to remove an electron that is farther from the nucleus

Try these . . .

•Which has a higher ionization energy: Na or Cl

Chlorine •Which has a lower ionization energy: Li or O

Lithium

Electronegativity

•The ability of an atom to attract electrons to itself

The Trend: electronegativity

INCREASES across a period •Why?•atoms are trying harder to attract electrons to get a full octet

The trend: electronegativity

DECREASES down a group

•Why?

•it is harder to hold on to the electrons that are farther away from the nucleus

Try these . . .

•Which element is more electronegative? F or Br

Fluorine•Which element is more electronegative? B or Ca

Boron

Finished!