Transcript Atomic size - McKnightScience

Catalyst – October
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2
(2 -2),
2009
Objectives
SWBAT determine the trends for atomic size and
electronegativity.
Catalyst
What family is Calcium in?
What period is Rb in?
Who was the first person to leave spaces for undiscovered
elements on the periodic table?
How did Mosley’s periodic table differ from all of the
tables that came before his?
Today’s Agenda
Catalyst
 Finishing Families
 More secrets of the PT: Atomic Size and
Electronegativity
 Exit Question

Alkali Metals
Alkali metals are very reactive – even
with water!
Sodium + Water  EXPLOSION!
Alkaline Earth Metals
Alkaline Earth metals are also very reactive
 Shiny solids that are harder than Alkali
metals
 Alkaline Earth Metal Spotlight: CALCIUM

 Calcium
is essential for human life, especially in
maintaining bones and teeth
 Found widely in nature combined with oxygen
 Abrasives in toothpaste and emery boards

Magnesium Demo!
Boron’s Group

Gallium is a silver metal that literally melts in your
hand!
Don’t try this
yourself!
Carbon’s Group

Carbon is one of the most important elements on
Earth!
 There
is a whole branch of chemistry dedicated to
studying carbon – ORGANIC CHEMISTRY!
 If you are a science major in college, you will most likely
take Organic

Silicon is the second most abundant element on
Earth!
 Use
in computer chips and solar cells
 Found in quartz, sand, and glass
Nitrogen’s Group
Metals, nonmetals, and metalloids!
 Nitrogen, which you breathe, can form some
of the most explosive compounds known to
man
 Arsenic is a toxic substance that was used to
treat some illnesses back in the day
 Bismuth is used in fire sprinklers

Oxygen’s Group

Oxygen
 We
must breathe oxygen to survive…so it’s
pretty important
 Reacts with some of the noble gases

Sulfur
 Hydrogen

sulfide smells like rotten egg
Selenium
 Used
in solar panels because it can convert light
into energy
Halogens (Fluorine’s Group)


Fluorine (really fluoride)
is added to toothpaste
Chlorine gas is a deathly
green gas that was first
used as a form of
chemical WARFARE in
WWII
Noble Gases (Helium’s Group)

Noble gases do not react with other elements
very often – they are already “happy”
 They
can be called “inert” because they don’t
react
Neon is used in neon lights
 Helium Voice!

Transition Metals
Conduct electricity
 Can form different ions (We’ll learn more
about ions later!)
 Many found in nature – found all over the
world (map on page 200)
 Uses

 Found
in alloys, wires, plastics, etc.
 Your body needs trace (small) amounts many of
them
What is Atomic Size?

Atomic size is…
How
big an atom is
Also known as atomic radius
Graphing Atomic Size (Radii)

Draw a line graph
X-axis:
Element
Y-axis: Atomic Radii (picometers)
Part 1 – points = dots
 Part 2 – points = squares

Elements and their Atomic Radii (1)
1 picometer = 1 x 10-12 m
Element
Atomic Radius (picometer)
Hydrogen
37
Lithium
152
Sodium
186
Potassium
227
Rubidium
248
Cesium
265
Elements and their Atomic Radii (2)
1 picometer = 1 x 10-12 m
Element
Atomic Radius (picometer)
Lithium
152
Beryllium
112
Boron
85
Carbon
77
Nitrogen
75
Oxygen
73
Fluorine
72
Neon
71
What trend(s) do
you notice?
Atomic size DECREASES as you go across the Periodic Table
Atomic size INCREAESES as you go down the
Periodic Table
Atomic Size
Key Point #1: Atomic size increases as
you go down the periodic table and
decreases as you go left to right across
the periodic table.
Practice Problems

Rank the following elements in order of
increasing atomic size based on location on
the periodic table (smallest to biggest)
Fr, Sc, P, Pd
Magnesium, Hydrogen, Francium, Strontium
F, As, Tl, S
Fluorine, Sulfur, Arsenic, Thallium
Practice Time!
1.
2.
3.
T or F? Atomic size decreases as you move right across
the periodic table.
T or F? As you move down the Periodic Table, atoms get
smaller.
Rank the following sets of elements in order of increasing
atomic size (small  big).
Set A: Bh, Mn, Re, Tc
Set C: Y, Ti, Sg, Ta
4.
Set B: Sb, I, Ag, Ru
Rank the following sets of elements in order of
decreasing atomic size (big  small).
Set A: Cl, At, I, F, Br
Set B: Te, Xe, Sn, In
Set C: Rb, K, Sr, Ca
What is electronegativity?

Electronegativity is…
The
ability of an atom to attract
electrons to itself in a chemical bond
How much an atom wants electrons
Graphing Electronegativity

Draw a line graph
X-axis:
Element
Y-axis: Electronegativity
Part 1 – points = dots
 Part 2 – points = squares

Elements and their Electronegativity (1)
Element
Atomic Radius (Paulings)
Hydrogen
2.20
Lithium
0.98
Sodium
0.93
Potassium
0.82
Rubidium
0.82
Cesium
0.79
Francium
0.70
Elements and their Electronegativity (2)
Element
Atomic Radius (Paulings)
Lithium
0.98
Beryllium
1.57
Boron
2.04
Carbon
2.55
Nitrogen
3.04
Oxygen
3.44
Fluorine
3.98
What trend(s) do
you notice?
Electronegativity
Key Point #2: Electronegativity decreases as
you go down the periodic table and
increases as you go left to right across the
periodic table.
Practice Problems

Rank the following elements in order of
increasing electronegativity based on location
on the periodic table (smallest to biggest)
Mg, Sr, Be, Ra
Radon, Strontium, Magnesium, Beryllium
Cl, Si, Al, S, P
Aluminum, Silicon, Phosphorus, Sulfur, Chlorine
Practice Time!
1.
2.
3.
T or F? Electronegativity decreases as you move left
across the periodic table.
T or F? As you move down the Periodic Table, atoms get
more electronegative.
Rank the following sets of elements in order of increasing
electronegativity (small  big).
Set A: Bh, Mn, Re, Tc
Set C: Y, Ti, Sg, Ta
4.
Set B: Sb, I, Ag, Ru
Rank the following sets of elements in order of
decreasing electronegativity (big  small).
Set A: Cl, At, I, F, Br
Set B: Te, Xe, Sn, In
Set C: Rb, K, Sr, Ca
How does atomic size related to
electronegativity?
Key Point #3: Atomic size is indirectly related to
electronegativity
ATOMIC SIZE
As electronegativity
ELECTRONEGATIVITY
increases, atomic size
decreases!
Why is this relationship true?
Atoms with HIGH ELECTRONEGATIVITIES hold
their electrons very close!
 Sooooo, the atomic size decreases

High or low electronegativity?
Large or small atomic size?
Group Work Time!
Exit Question
1.
2.
3.
Which element has atoms with the
smallest size: Cl, Se, P, or F?
Which element has the largest
electronegativity: Ag, Cu, Hg, or
Zn?
What is the relationship between
atomic size and electronegativity?