Transcript Periodic Trends

Periodic Trends
Periodic Law
The statement that there is a periodic
repetition of chemical and physical
properties of elements when arranged by
increasing atomic number
Groups
Elements in the same group have the same
number of valence electrons.
Group 1 have 1 valence electron
Group 2 have 2 valence electrons
Group 13 have 3 valence electrons
Group 14 have 4 valence electrons
Why?
Problem
Without looking at the periodic table,
determine the group, period and block in
which strontium is located.
[Kr] 5s2
Group: superscript 2 = valence electrons
Period: coefficient of 5, so 5th period
Block: s-block
Ion
an atom or bonded group of atoms that has
a positive or negative charge
Ionization energy
the energy required to remove an electron
from a gaseous atom
Octet Rule
States that atoms tend to gain, lose or share
electrons in order to acquire a full set of
eight valence electrons
Electronegativity
Relative ability of atoms to attract electrons
in a chemical bond
Noble Gas
An extremely unreactive group 18 element
Valence Electron
The electrons in an atom’s outermost
orbitals
Determine the chemical properties of an
element
Make squares
Periodic Trend
Atomic Radius
Ionic Radius
Ionization
Energy
Electronegativity
Period
Group
Atomic Radius
Atomic size is defined by how closely an
atom lies to a neighboring atom.
Decreases left to right across a period
Atomic mass increases left to right
Atomic mass increases as you go down
Atomic mass increases as you go down
Which has the largest atomic
radius?
Carbon, fluorine, beryllium, or lithium?
All 4 elements are in period 2, so write in
order across the period
Li, Be, C, F
Lithium is first, so it has the largest radius
Ionic Radius
Atom loses electron(s)
becomes positive
decreases in size
Atom gains electron(s)
becomes negative
increases in size
Why?
Lose valence electrons gives empty outer
shell
Electrostatic repulsion among the remaining
electrons decreases and they are pulled
closer to the nucleus
Add electrons, increases electrostatic
repulsion, forcing electrons further apart
Ionization Energy Trends
Increases left to right across a period
Decreases when you move down a group
less energy to remove valence electrons
bc they are farther from the nucleus
Octet Rule
Atoms want a full set of 8 valence electrons
First period is the exception bc only have 1
or 2 electrons
Predict
What part of the periodic table has the
greatest electronegativity.
Upper right
Squares
Periodic Trend
Period
Group
Atomic Radius
 Left to right
 down
Ionic Radius
 Left to right
 down
Ionization
 Left to right  down
Energy
Electronegativity  Left to right  down
Electron-dot Diagram
Calcium
Aluminum
Arsenic
Tellurium
Xenon
Resource
http://www.docbrown.info/page03/3_34ptabl
e.htm