CHEM Unit 4 - Periodic Table & Trends

The First Periodic Table

created by Dimitri Mendeleev who arranged the elements in otder of increasing atomic mass

The Rearrangement of the Periodic Table

Henry Mosley rearranged the elements in order of atomic number

Why did Mosley rearrange the PT?

he determined that it is the atomic number(protons), not the weight of the element that determines the elements’ chemical properties(bonding potential)

Periodic Law

When elements are arranged in order of increased atomic number, there is a periodic repetition of their chemicals and physical properties.

Groups

vertical columns
tell us how atoms chemically react based on the number of valence electrons

elements in the same group have similar chem properties

Groups’ Representation of Valence Electrons

for 13-18, ignore the 1

Periods

horizontal rows
tell us how far the electrons are from the nucleus

represent the # of energy levels

Periods’ Relation to F

there are 7 periods

4f and 5 f don’t count

Main Group Elements

groups 1,2,13-18

have the same # of valence electrons and bonding potential

each mge forms the same charge when forming ions

Group 14 Charge

+-4
to the right +, to the left -

Metals

left of staircase
good conductors of heat and electricity
malleable
ductile

Malleable

can be pounded in thin sheets
ex. Al foil

Ductile

can be drawn into thin wires
ex. copper wire

Non-Metals

right of staircase
poor conductors of heat and electricity
brittle

gases

Brittle

solids that break easily

Metalloids’ Locations

elements that touch the staircase, except aluminum

Metalloids’ Definition

has properties of metals and non-metals

Group 1

Alkali Metals
the most reactive metals due to having 1 ve
with 1 ve, increased desire to bond with another atom
reacts violently in pure water

Group 2

Alkaline Earth Metals
2nd most reactive metals with 2 ve
2 electrons likely to leave and bond with another atom

Group 17

Halogens
most reactive nonmetals due to having 7 ve
1 e shy of full outer shell, increased desire to bond with another atom and gain 1 e

Salt Makers

group 17
any metal bonded with a halogen forms a type of salt

Group 18

unreactive with a full outer energy level that satisfies duet/octet rule
rarely bonds with other atoms

Block D

transition metals

Periodic Trend

specific pattern in the properties of chemical elements that are revealed in the periodic table of elements

Group Trend

a pattern of change as you move down a group

Period Trend

a pattern of change as you move across a period

Atomic Radius Affecting Factors

nuclear charge and increasing energy level

Nuclear Charge

the pull of protons in the nucleus on the electrons in the outer electron cloud

Atomic Radius Arrows

I down D right

Atomic Radius Group Trend

as you go down a group, the atomic radius increases, atoms get bigger due to the increase of energy levels

Atomic Radius Period Trend

As you move across the period(same energy level) the atomic radius decreases, atoms get smaller due to a higher nuclear charge. The increased protons pull the electrons in toward the nucleus, making the atom smaller

Ionization Energy

the energy (kJ/mol) needed to remove the most loosely held electron on the valence shell

each electron requires more energy

Ionization Energy Group Trend

as you move down a group, ionization energy decreases 

easier to remove an outer electron from a bigger atom

these outer electrons are further away from the nucleus and are less attracted to the protons

Ionization Energy Period Trend

as you go across a period, ionization energy increases
it is harder to remove an outer electron from a smaller atom
these outer electrons are closer the nucleus and more attracted to the protons

Ionization Energy Arrows

D down I right

Electronegativity

the tendency for an atom to attract electrons in a chemical bond

Pauling Scale

measures electronegativity by assigning atoms a value 0.0 - 4.0

Electronegativity Group Trend

as you move down a group, electronegativity decreases
The ability to attract an electron decreases as the atom gets bigger
The nucleus charge is weaker

Electronegativity Period Trend

as you move across the period, electronegativity increases
The ability to attract an electron increases as the atom gets smaller
The nuclear charge is stronger

Electronegativity Arrows

D down I right

Cation

ions with a positive charge, that lose electrons to be isoelectronic with a noble gas

Anion

ions with a negative charge, that gain electrons to be isoelectronic with a noble gas

Cation Size

Cations are smaller than their neutral atom since they lose an entire energy level
ex. Na = 11e, Na+1 = 10e

Anion Size

anions are larger than their neutral atom since they fill out their outer energy level