Period Table
Organization & Trends
Mr. O’Brien (SFHS)
Chapter 6
Standard 1B &C
How Atoms Differ
std.1A(review)
• The number of protons in an atom
(Atomic Number) identifies a particular
atom.
– Atomic number = number of protons =
number of electrons
– The Periodic Table organizes all known
elements by increasing atomic number.
• Isotopes: Atoms with same number of
protons but different number of
neutrons.
– ex: in potassium, 93.25% of the K atoms
has 20 neutrons, 6.73% has 22 neutrons,
0.01% has 21 neutrons.
• Mass Number: sum of protons and
neutrons in the nucleus.
– Mass Number = Atomic number – neutron
number.
• Atomic Mass:weighted average mass
of the isotopes of that element.
– (a.m.u.) mass standard 1/12 of C
Valence Electrons & Ions
•
std.1D(review)
Valence electrons
1. Electrons in the outermost orbital.
2. Group # represent amount of valence electrons.
3. Atoms in the same group have similar chemical properties because they
have same # of valence é
4. Atoms gain or lose valence electrons for bonding
•
Octet rule: Atoms tend to gain, lose, or share e in order to acquire a full
set of eight valence é (noble gas).
–
–
•
Ion: an atom that gains or lose ve to have a positive or negative charge.
–
–
•
Exception (helium)
Having all their valence é (8) make noble gases stable!
When atoms lose ve and form positively charged ions (cations)
When atoms gain ve, they form negative charged ions (anions).
Practice:
–
–
–
How many electrons will oxygen gain/lose to become a noble gas?
Identify the number of valence electrons for bonding in Magnesium.
Identify the number of electrons chlorine can accept for bonding.
All elements want to be like a Noble Gas
Organization of the Periodic Table
(std.1B)
• How is the periodic table organized?
– Arranged by increasing atomic number.
• What do we call the columns & rows?
– Groups/ Family = columns ↕
Key Term
Representative Elements
Groups labeled with A (1A-8A)
– Periods = rows ↔
• periods can also represent the energy
levels
Checking for Understanding
Identify the Element:
1. Group 1 Period 1
2. Group 2 Period 2
3. Group 15 Period 3
(figure 1) The images above and below show the
distinction between groups and periods. Note groups
(families) are indicated by the # of valence electrons
and periods by the principle number.
•
Organization of the
Periodic Table (std.1B)
What are the 3 types of Elements?
– metal
• elements that are SHINY, SOLID, GOOD
CONDUCTORS of electricity and heat,
MALLEABLE, HIGH melting points, and
DUCTILE.
Organization of the Periodic
Table (std.1B)
• What are the 3 types of Elements? (cont.)
– metalloid (semi-metal/semiconductors)
• Generally behave as non-metals but conductivity
resembles metals.
• “stair-step line” visual divider between metals and
non-metals.
• Many transistors and other computer chips are made
from silicon or germanium (semi-conductors).
Organization of the Periodic Table
(std.1B)
• What are the 3 types of Elements? (cont.)
– non-metal
• mostly gases and soft solids, poor conductors of
electricity and heat (insulators), elements that are
gases, BRITTLE, and poor conductors.
Bromine
(liquid)
Chlorine (gas)
Checking for Understanding
1. What are the majority of elements on the PT?
2. An element is malleable, were would it be located?
3. I am used in computer chips and located in Group 4A.
Sulfur (brittle solid)
•
Alkali metals
–
–
–
•
group 3-12 between period 4-7
forms various + charges
group 16/6A
gains 2 valence é (forms ions with -2 charge)
Halogens
–
–
–
•
group 2/2A
lose 2 valence é (forms ions with +2 charge)
Chalogens
–
–
•
(std.1B)
Transition metals
–
–
•
Family Names
Alkaline earth metals
–
–
•
group 1/1A
most reactive metal group
lose 1 valence é (forms ions with +1 charge)
group 17/7A
most reactive non-metal group
gains 1 valence é
Noble Gases
–
–
Checking for Understanding
1.
Identify the most unreactive element in period 3.
2. Identify a period 4 Alkaline Earth Metal.
3. I am the most reactive non-metal in period 5.
group 18/8A
most stable (unreactive) group in the entire
periodic table.
(figure 3) Above. Two of the Halogens
are gas (F, Cl) and the other two,
liquid (Br) and solid (I). Fluorine is the
most reactive!
(figure 2) Right. Alkali metals are
stored in oil because they are so
reactive! The picture at the bottom
right shows reaction with rubidium in
water; explosion of bath tube.
Family Names (cont.)
Honors Info
•
Lanthanide Series:
– Found mixed together in nature. Hard
to separate. “Rare Earth” elements
•
Actinide Series:
– Radioactive elements
– Most are synthetically made in particle
accelerators.
• Those above atomic # 92
• Known as Transuranium elements
•
How do particle accelerators work?
– particles are accelerated (protons, or
electrons) to very high speeds.
– These particles smash stationary metal
objects or collide against other moving
particles
– The result are new atoms produced.
(figure 3) left. Rare
mineral “Bastnasite”
contains metals
Lanthanide and
Cerium .
(figure 3) left.
Simulated particle
collision.
(figure 1) left. The circular particle
accelerator at CERN near Geneva. It’s
circumference is about 15.9 miles long.
(figure 2) above. The tunnel inside the
CERN accelerator.
Periodic Trends
(std.1C)
 What are the Trends (patterns) on the
Periodic Table?
• Atomic Radius (size of an atom)
– Period (trend): Increases size from Left to
Right.
– Group (trend): Increases from Top to
Bottom
• Ionic Radius (size of an ion)
• When comparing atoms with their ions:
• (+ ions) are always smaller (than their
atom) because they lose valence é.
• (- ions) are always bigger because they
gain valence é.
(figure 3) Notice the trends of the
ion sizes are essentially the same
as the atomic radius trend.
(figure 2) Above. The image shows the
relative size of an atom and its +/- ions.
When sodium atom loses an é, the ion
gets smaller because there are more
protons pulling in fewer electrons.
Conversely, when the chlorine atom
gains an é, the ion becomes larger
because there are more electrons than
protons.
Periodic Trends (std.1C)
 Ionization energy:
 energy it takes to remove an electron
from an atom.
• Trends within periods:
• Increases as you move from left to
right across a period.
• Trends within groups:
• Generally increases as you move
up a group.
 Electronegativity:
 ability of its atoms to attract é in a
chemical bond.
• Trends within periods:
• Increases as you move left to right
across a period.
• Trends within a group:
• Increases as you move up a group.
Checking for Understanding
1. Which group requires the most energy to take away an electron? Which
requires the least?
2. Which group on the periodic table is the most electronegative? Explain
Periodic Trends (std.1C)
Practice
1.
Which group on the periodic table has the lowest
ionization energy. Explain why that is so.
A.
2.
Which has the largest atomic radius: nitrogen (N),
antimony (Sb), or arsenic (As)? The smallest?
A.
3.
Noble gases have a full set of valence e so they will
not lose any valence é. As a result noble gases are
very unreactive.
(figure 1) Shows ionization energy of elements
across the periodic table.
Why does ionization energy decreases as you go
down a periodic table?
A.
5.
Antimony is the largest atom; nitrogen is the smallest.
Explain why noble gases have the highest ionization
energy.
A.
4.
Since Alkali metals have very low ionization energy
they lose valence é to form (+) ions.
Since the atom increases in size as you go down the
group, the valence é are further away from the
nucleus. It becomes easier to take away a valence é
that is further away.
Explain, using electronegativity, why Halogens form
(-) ions.
A.
Since Halogens have high electronegativity values,
they will attract valence é from others. When it gains a
valence é they become (-) ions.
(figure 2) Shows ionization energy of elements
across the periodic table.