Transcript Atoms and the Periodic Table

The Nature of Matter
Physical Sciences
Benchmarks
A. Describe that matter is made of minute particles called atoms and
that atoms are comprised of even smaller components. Explain
the structure and properties of atoms.
B. Explain how atoms react with each other to form substances and
how molecules react with each other or other atoms to form even
different substance.
C. Describe the identifiable physical properties of substances (e.g.,
color, hardness, conductivity, density, concentration, pH, and
ductility). Explain how changes in these properties can occur
without changing the chemical nature of the substance.
H. Trace the historical development of scientific theories and ideas, and
describe emerging issues in the study of physical sciences.
Defining Matter
Matter - anything that has mass and takes up space.
Mass - the total amount of material in an object.
Tool to measure - triple beam balance
Units - mg, g, kg, etc.
Defining Matter
Volume - the amount of space an object occupies.
The volume of liquids can be measured using a
graduated cylinder or beaker.
Units are liters (L) or milliliter (mL).
The volume of irregular shaped objects are measured using
water displacement with a graduated cylinder or beaker.
Units are liters (L) or milliliter (mL).
Defining Matter
The volume of a cube can be calculated by measuring the
length of one side using a meterstick or ruler.
V = length X height X width
Ex.: If the length of one side of a cube is 2 cm, what is the
volume?
V = 2 cm X 2 cm X 2 cm
V = 8 cm3
Defining Matter
Density - the amount of matter in a given space.
D = mass / volume
Mass and volume both need to measured separately! The calculation
(ratio) of the two measurements equals the density.
Ex.: If the mass of a cube is 54 grams and the length of a side is 3 cm.,
what is the density of the cube?
First solve for volume: V = L X h X w
V = 3cm X 3cm X 3cm
V = 27 cm3
Density = mass =
volume
54 g
27 cm3
= 2 g/cm3
Chemistry
Elements - the building blocks of matter, a pure substance, made up of one
type of atom.
Atom - the smallest particle of an element that has the properties of that
element.
Substance - made up of one or more elements.
Compound - a combination of two or more atoms that maintains its own
properties.
Molecule- smallest particle of a substance that retains all the properties of
the substance and is composed of one or more atoms.
Composition - what matter is made of and how it is organized
Chemistry
Properties - describes the characteristics, composition and behavior of matter,
including the changes that matter undergoes.
1. Physical - characteristics that a sample of matter exhibits without any
change in its identity. Solubility, melting point, boiling point, color, density,
electrical conductivity, physical state.
2. Chemical - can be observed when there is a change in the
composition of the substance. Iron at room temp with air = iron oxide
(rust).
Chemical formula- shows the number and kind of elements in a substance
2NH3
Coefficient
(number of molecules)
subscript
(number of atoms)
Classifying Reactions
• Synthesis Reaction- Reaction in which two or more substances
combine to form a compound.
2Na + Cl2 ------ 2NaCl
• Decomposition Reaction- Compound breaks into two or more
substances. 2HgO ------ 2Hg + O2
• Single Replacement Reaction- One element replaces another
element in a compound to form a new compound
Fe + CuSO4 ----- FeSO4 + Cu
• Double Replacement Reaction- Occurs when two compounds
in a reaction exchange ions
AgNO3 + NaCl ----- AgCl + NaCO3
History
Greek philosophers (Democritus) created theories about
indivisible matter: “Atomos” - meaning that which
cannot be cut or divided.
Aristotle theorizes that everything is composed of Earth,
Water, Air, and Fire.
History
Early 1800’s, John Dalton created the atomic theory: (4 parts)
1. All elements are made up of atoms. Atoms cannot be created, divided,or
destroyed.
2. All atoms of the same element have the same size and mass.
3. Atoms of different elements have different sizes and masses.
4. During a chemical reaction, atoms are not destroyed, just rearranged.
Nuclear power disproves theorem number one. (Fission and Fusion)
Periodic Table
History of the Periodic Table
• Antoine LaVoisier
 1790’s
 Complied a list of the 23 known elements at
the time…
• Most of the 23 had been known since as
early as prehistoric times
 Cu, Pb, Au, Ag, Fe, C, S, Zn, Hg, As
 Sb, Cr, O, P
History of the Periodic Table
• Lothar Meyer(German)/ Dmitri Mendeleev (Russian)
 1869
 Noticed connection between atomic mass and properties
 Mendeleev gets more credit – he got published first- AND
could better demonstrate the tables usefulness
• Mendeleev was able to predict the properties of
undiscovered elements
The Periodic Table
• Henry Moseley
 1913
 Found slight problems with Mendeleev’s periodic table
 Arranged elements in order of atomic number instead of
atomic mass
• Flip-flopped some elements (Ex – Cu and Zn)
 Resulted in clear patterns and properties
www.chemicalelements.com/
The Periodic Table
3. Elements in columns are called groups or families
a. Total of 18 groups
b. Groups have same characteristic and # of valence electrons
1. Ve-: electrons in outer shell
c. as elements descend atoms grow larger
4. Elements in rows are called series or periods
a. elements are arranged by inc. # of protons (atomic #)
b. Total of 7 periods
c. Descending periods increase electrons in shells. This is due to
increasing mass.
d. As one goes across period atoms grow smaller.This is due to force of
charge pulling in electrons.
Atomic Mass and Numbers
Atomic Number – number of protons
Number of protons determines the
number of electrons in a neutral atom.
Atomic Mass – number of protons and
neutrons
Atomic mass minus atomic number
equals the number of Neutrons.
The Periodic Table
Atomic
Number
3
Symbol
Li
Name
Lithium
Atomic
mass
6.941
Lithium
Protons=3
Electrons=3
Atomic
Mass=6.941
Neutrons=4
Element Sizes
Electron Configurations
These are the most stable arrangement of electrons
There are 4 regions: s,p,d,f
s holds total of 2 electrons ___
p holds total of 6 electrons ___ ___ ___
d holds 10 electrons ___ ___ ___ ___ ___
f holds total of 14 electrons ___ ___ ___ ___ ___ ___ ___
Shells will fill up one at a time (like seats on a bus)
Electron Configurations
• Most stable arrangement of electrons
• 1s2
-The large number "1" refers to the principle quantum number "n" which stands for the
energy level. It tells us that the electrons of helium occupy the first energy level of the
atom.
-The letter "s" stands for the angular momentum quantum number "l". It tells us that the
two electrons of the helium electron occupy an "s" or spherical orbital.
-The exponent "2" refers to the total number of electrons in that orbital or sub-shell. In this
case, we know that there are two electrons in the spherical orbital at the first energy
level.
Oxygen: O 1s22s2 2p6
Bohr’ Models
• Model that illustrates subatomic particles for an element
Step 1: calculate total number
subatomic particles
Step 2: Create the nucleus by
drawing protons and
electrons
Step 3: Create electron shells
and attach the correct
amount of electrons
Step 4: Label all particles and
shells
Particle behavior
Hund’s Rule: electrons are negative, they have same
charge and repel from each other, as far apart as possible.
Heisenberg Uncertainty Principle: 1920,
impossible to measure accurately both the
position and energy of an electron at the
same time.
Atomic Structure
Subatomic Particles: the particles below the surface of an
atom. This includes protons, neutrons and electrons. An
electrical force between nucleus and electrons holds the
atom together.
atom: smallest particle of an element that has the
chemical properties of that element.
1. a billion atoms laid end to end would make a
line only 10cm long
2. atoms make up cells
Atomic Structure
A. electron: negatively charged particle orbits the nucleus
1. electron is first to be discovered - 1891
2. lightest subatomic particle
B. proton: positively charged particle
1. located in nucleus of atom - 1896
2. second lightest subatomic particle
C. neutron: neutrally charged particle
1. located with proton in nucleus - 1932
D. nucleus: holds protons and neutrons of atom
1. discovered in 1910
2. atoms are mostly empty space,distance between nucleus and electron
is like a marble on the pitchers mound of a baseball field and the
furthest seat in the stadium would be the electron.
Atomic Models
Electron Cloud
Bohr’s Model