Unit 1 Test Reminder
A Unit 1 Practice Test, self-evaluation sheet, and a review sheet have been posted on Sharepoint. Please read through the review sheet carefully; most of your questions will be answered there.
Warmup (5 minutes)Silicon has three stable isotopes in nature as shown below. Find
the missing information.
Mass of Silicon Isotope % Abundance of Si Isotope
27.98
4.70
29.97 3.09
av.atm.ma Si = (27.98)(0.9221) + 0.0470x + (29.97)(0.0309)
28.09 = 25.800358 + 0.0470x + 0.92607
1.36357 = 0.0470x
x = 29.01 amu
x92.21 0.9221
0.04700.0309
The Periodic Table and Electron Diagrams
A chemistry student wished to make some potassiumhydroxide solution and decided to throw a large
lump of potassium into a bucket of water. Her professor observed what she was about to do, out of the corner of
his eye and hurried towards her.After confirming this was what she was intending to do, he asked her first to stir the water in the bucket for five minutes before adding the potassium. She was puzzled
and ran after him to ask the purpose of this action.
“It will give me time to get away” said the professor.
Today you need paper for notes, your PT and maybe
some colors….
Periodic Table Development In the mid 1800’s there was no organization of the
known handful of elements. It was difficult to find information, and chemistry didn’t make sense.
In 1869, Dimitri Mendeleev arranged the elements in rows according to increasing atomic mass and in columns according to the way they reacted
In 1913, Henry Moseley filled in the blank spaces, and revised the PT based on atomic number
I’m the MAN!
I’m pretty studly
myself!
G
R
P E R I O D O
U
P
How many
*groups
*periods
are there?
*period/series: horizontal row; as you move left or right, properties of the element change
group/family: vertical column; elements share
many of the same physical and chemical
properties
IA VIIIA
IIA IIIA IVA VA VIA VIIA
2
1
3 – 12 or B group metals
13 14 15 16 17
18
Look carefully at the 2 ways that the groups on your PT is numbered
Li3
Na11
K19
Rb37
Cs55
Fr87
Group IAsoft, shiny, very
reactive with water and air
*hydrogen is not part of this group
I
BeBe
RaRa
MgMg
CaCa
SrSr
BaBa
Group IIA*reactive, but less reactive than alkali
*harder, more dense
*always combined with nonmetals in nature
* many are important mineral nutrients
Transition metals: The bling bling metals
Lanthanides
Actinides
Bi
Sn
Al
Ga
Less reactive, hard metals Jewelry/construction. Metals used “as metal.”
Metals are: Good conductors of heat and electricity
Malleable (easily flattened)
Ductile (can stretch it into a thin wire)
Have luster (shiny)
Silvery
Use a marker to OUTLINE the metals
Metalloids or SemimetalsHave properties of both metals & nonmetals
B
At
Color in the semimetals, outline the nonmetals as
one large unit for right now (do not color)
Metals vs. Nonmetals vs. Metalloids
MetalMetalloid
(Semimetal)Nonmetal
Good conductors of electricity and
heat
Okay conductors of electricity and
heat.
Poor conductors of electricity and heat
Shiny (luster)Can look shiny or
dull.Not Shiny
MalleableCan be malleable
or brittle.Not Malleable
(brittle)
Most are SOLID at room temp.
All are SOLID at room temp.
Most are GAS at room temp.
Group VIIA
Br Br
I I
Cl Cl
F F
mostly colored & gaseousvery reactive, combine with metals to form salts
Periodic TableGroups
Semimetals NonmetalsMetals
Alkali MetalsAlkaline Earth
MetalsTransition
MetalsHalogens Noble Gases Other
(Family)
C, N, O P, S, Se, H
The Periodic Table and Valence Electrons
Remember that Mendeleev grouped elements according to similar chemical and physical properties!
What CAUSES some elements to have similar chemical properties?
Same number of valence electrons, same kinds of ions, similar reactivity.
But what is a valance electron, how are they
different than ‘regular’ e-, and how do I know how
many an atom has?
What are valence electrons?
electrons found in the outermost energy shell.
only valence e- interact with other atoms in chemical reactions (inner e- are shielded)
only the raincoat gets wet; your sweater, and shirt stay dry.
Valence Shell
Bohr Electron Diagrams- technically NOT entirely accurate.
- improved upon with the addition of more information- but since it is easier to learn from…we will use this
model to understand how electrons work!
1st shell: holds 2 e-
2nd shell: holds up to 8 e-
3rd shell: holds up to 8 e-
**Other shells (energy levels) hold more electrons, we won’t get into this!
e-
e-
e-e-
e-
e-
e-e-
e-e-
e-
e-e-
e-e-
e-
e-e-
e- are restricted to energy levels around a nucleus.
This is the e- arrangement of WHICH
neutral element? Ar, group 8A
Beryllium – 9
4 P5 N
e-
e-
e-
e-Steps: Bohr Electron Diagrams
1. How many protons and neutrons?
2. How many electrons? (assume neutral).
3. Filling first energy shell…maximum two e-
4. If needed, fill out the second energy shell. Space apart the first 4 e-, then pair them up. In which group is this
element?
valence electron (Lewis dot) diagrams
Ex. Lithium - 6
3 P3 N
e-
e-e- Li
In which group is this
element?