
late 1790’s Antoine
Lavoisier made a list of
known elements
◦ contained 23 elements

1864 John Newlands
looked further into
organization
◦ The Law of Octaves –
repeating trends every 8
elements


Late 1800’s Russia
Grouped elements with similar properties into
columns
◦ 7 columns were formed
 Noble Gases (8th Column) were later discovered


Was able to predict properties of missing
elements
When Germanium was discovered, it fit his
predictions

Does mass always increase throughout the
periodic table?
◦ NOPE





Tellurium (52)
Iodine (53)
Nickel (28)
Argon (18)
Potassium (19)

The properties of the elements are a periodic
function of their atomic masses
◦ periodic means repeating, like the moon cycle,
every month it repeats

**atomic number was not known during
Mendeleev’s time


The properties of the elements are a periodic
function of their atomic numbers
Using x-rays, Henry Moseley determined the
number of protons per element
◦ This is Atomic Number

Elements with similar e- configurations are in
the same columns known as “groups” or
“families”
◦ Families  familiar characteristics
◦ Families have the same number of v.e.’s

Rows are periods, each row designates a
different nrg level
Columns are groups or families and contain

Notable rows and columns

elements with similar properties
◦ Rows:
 4f – Lanthanides
 5f - Actinides
◦ Columns:




1 or IA – Alkali Metals
2 or IIA – Alkaline Earth Metals
17 or VIIA – Halogens
18 or VIIIA – Noble gases

“A” Groups

Filling the ‘s’ and ‘p’ sublevels

Contains both metals and non metals

“B” Groups

Fills the ‘d’ sublevels

Made up of only metals



Fill the ‘f’ sublevels
Lanthanides
Actinides

Luster (shine)
Ductile (pulled into wires)
Malleable (hammerable and won’t shatter)
Good conductors of heat and electricity

Have 3 or less v.e.’s so they tend to lose them



◦ Usually no more than 3 v.e.’s

Includes transition metals, actinides and
lanthanides



Brittle (most are gaseous)
Good insulators, not typically good
conductors of heat or electricity
Have 5 or more v.e.’s, so they tend to gain (or
share) e-’s




Elements with properties of both metals and
nonmetals
Located on the diagonal between metals and
nonmetals
There are 8 metalloids
Can lose or gain v.e.’s depending on their
placement on the periodic table

8 e- in the outer nrg level make an atom not
reactive or stable
◦ Metals lose their e-’s to achieve octet
 They become positive ( + ) = cations
◦ Families 15 (VA), 16 (VIA), 17 (VIIA) gain e- to
achieve octet
 They become negative ( - ) = anions

All elements WANT 8 e-’s to become stable


The most active metals are in the lower left
corner of the periodic table
The most active nonmetals are in the upper
right corner of the periodic table
Most
active
Reactivity
F
nonmetal
Decreases
Most
active
metal
Fr
Reactivity
Decreases
Periodic Trends

Increases as you go down a group
◦ More e- = bigger radius
◦ Atoms are gaining nrg levels

Decreases as you go across a period
◦ e- are being added to the same nrg level
◦ Nuclear charge – force of attraction between e- and
nucleus
◦ As you move across a period, more e- are being
attracted to the nucleus



INCREASES as you go DOWN a group because
of nrg levels
DECREASES as you go ACROSS a group
because of nuclear charge
Noble gases radii are found to be larger
because they don’t interact with other atoms
of the same element as most others do.

Atoms can lose or gain e- to complete or
empty an outer nrg level
◦ Every atom wants an octet


Ion – an atom that has a + or – charge
Metals
◦ Lose e- giving them a + charge
◦ Decreases their radius
◦ These are cations

Nonmetals
◦ Gain e- giving them a – charge
◦ Increases their radius
◦ These are anions

Cations
◦ H+, Li+, Na+, Mg2+, Ca2+

Anions
◦ F-, Cl-, O2-, S2-, N3-, P3-


**noble gases don’t have ions, they are stable
and DO NOT IONIZE
*carbon doesn’t ionize a lot, it “shares”
◦ When it does ionize, it gains 4 e Sizably increases its radius

Nrg needed to remove an e- from an atom
◦ Unit = (kJ/mol)

ACROSS a period, it INCREASES
◦ Due to increase in nuclear charge

DOWN a group, it DECREASES
◦ Due to increased atomic radius and shielding effect


Metals = low I.E.
Nonmetals = high I.E. (especially noble gases)

Nrg needed to remove a second e- from an
atom
◦ Typically harder to remove a 2nd e-
Be
1s
2s
2p
B
1s

2s
2p
More stable,
full/empty
sublevels
Less stable,
partial sublevels
**The higher the I.E., the more stable the atom.

The power of an atom in a molecule to
ATTRACT e- to itself
◦
◦
◦
◦

Ability to “hold on to e- more”
DECREASES from top to bottom of group
INCREASES from left to right in periods
F has the highest E.N.
High E.N.’s gain e- and form (-) ions
◦ The more stable an atom, the less likely it will
attract an e Would result in (-)E.N.

High E.N. = High electron affinity

Like tug-o-war
◦ Big guy (high E.N.)
◦ Little guy (low E.N.)
Decrease in E.N.
Decrease in E.N.
F

Most active metals (lower left) have the
LOWEST E.N.

Fluorine has the highest E.N.

Noble Gases have NO E.N., because they
don’t typically bond

No units for E.N. because it is a comparison

Deals with compounds and bonding