Periodic Trends

Mendeleev(1869)

organized the elements by increasing atomic mass and so that elements in the same row have similar properties

Moseley(1913)

rearranged the elements by increasing atomic number

this is how the modern periodic table is arranged today

Periodic Law

When elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties

Period

Group

horizontal rows of the table

vertical columns on the table

In the same group

similar properties

numbered 1-18

In the same period

doesn’t not have similar properties

numbered 1-7

same number of occupied energy levels

s block

representative elements

p block

representative elements

d block

transition metals

f block

inner tradition metals

Metals

left of staircase

lustrous(shiny)

malleable: hammer into thin sheets

ductile: make into thin wire

good conductors of heat and electricity

Nonmetals

right side of the staircase(hydrogen included)

non-lustrous(dull)

brittle: breaks easily

poor conductors good insulators

Metalloids

Touch the staircase and have properties of both metals and nonmetals with the exception of aluminum. It is a metal.

they are semi conductors, which means they normally do not conduct electricity, but will conduct at high temperatures or when certain substances are added

Atomic Radius

An atom does not have a fixed radius. The radius can only be found by measuring between two nuclei of two touching atoms then halving that distance.

½ of the distance between the nuclei of two like atoms

it is dependent on nuclear charge(magnitude of attraction from nucleus) and distance between electrons and nucleus

Period Trend

Group Trend

decreases left to right—greater number of protons

increases down—greater number of occupied energy levels

Shielding Effect

the inner electrons shield or block the attraction from the nucleus.

while, there is not an increase in number of protons down a group. This does not affect the magnitude of attraction from the nucleus due to this effect.