Download Ch 3 Outline- Intro to Atom and Periodic Table

Ch. 3 The Atom and Periodic Table of Elements
1. Atomic Theory
a. Democratus-proposed that matter was formed from small pieces that couldn’t be cut into
smaller parts. (439 BC)
b. Used the word atomos, which means “un-cuttable”.
c. The idea of an “atom” being the smallest particle of matter developed in 1600s as more
scientists experimented and gathered evidence. As evidence increased, the theory and model
of an atom changed.
i. Dalton’s Atomic Theory--“smooth hard balls” with the following characteristics:
1. Elements consist of atoms that cannot be divided—no sub atomic particles.
2. Atoms of the same element have same mass, particular to that element.
3. Atoms of one element cannot be changed into an atom of a different element by
a chemical reaction—not turning lead into gold.
4. Compounds form when atoms of more than one element combine in a set ratio.
ii. Thomson’s Model—“seeds in a watermelon”
1. Discovered electrons—negatively charged particles, disproving #1 above and
Dalton’s whole theory.
2. Decided that if atoms have a negative particle, then they should also have a
positive particle to balance it out.
iii. Rutherford’s Model—“cherry with a pit in the center”
1. Discovered that an atom has a nucleus that is positively charged.
2. Discovered that the positively charged particles in the nucleus—called protons.
iv. Bohr’s Model—“electrons like rings of a tree”
1. Electrons found only in specific orbits around the nucleus like the planets orbit
the sun.
2. Electrons move at a specific speed with a fixed energy
v. Cloud Model— “cloud”
1. Electrons move rapidly in a cloud around an atom’s nucleus.
2. Electrons move according to their energy level. Electrons with different energy
levels would be found in different places within the cloud.
vi. Modern Model
1. James Chadwick discovered neutrons —particles without any charge 1932
2. Tiny dense nucleus composed of protons and neutrons surrounded by a moving
cloud of electrons
a. Cloud is much much larger than the nucleus.
3. Particle Charges
a. Protons (+)
b. Neutrons
c. Electrons (e-)
4. Neutral atoms—no electrical charge because…
a. The number of protons and neutrons within a nucleus are usually the
same.
b. The number of protons and electrons are usually the same.
5. Particle Masses
a. Electrons much tinier much less dense.
electrons=mass of 1 proton)
b. Atoms measured in atomic mass units (amu)
i. One proton / neutron = approx. 1 amu
(1840
6. Atomic Number- the number of protons in the nucleus of an atom.
a. Every specific type of atom has the same number of protons.
7. Isotope- An atom of a certain element that has a different number of neutrons
than protons. It’s still that element, but a different form of it.
Carbon-12
6 protons
6 neutrons
6 electrons
(neutral)
Carbon-13
6 protons
7 neutrons
6 electrons
(isotope)
Carbon-14
6 protons
8 neutrons
6 electrons
(isotope)
8. Mass Number—Sum of protons and neutrons in an atom
2. Mendeleev’s Work
a. Knew some elements had similar chemical and physical properties
Example: silver and copper are different elements and are both shiny.
b. Suspected elements could be organized into a pattern based on their properties, atomic mass,
and the way these elements reacted to other elements.
i. Periodic Table of Elements—organzes elements based on the patterns of their
properties.
1. Contains information:
19 protons in nucleus
19
a. Atomic Number
K
b. Chemical Symbol
Potassium’s
chemical symbol
39.098i.
c. Atomic Mass
Protons + Neutrons
3. Periodic Table of Elements
a. Organization- Useful because an element’s properties can be predicted from its location on the
periodic table.
i. Periods- 7 Rows / 7 Periods
1. A period contains different elements
2. Properties change on the table from left to right.
3. Metals on the left and non metals on the right.
a. Metalloids found between metals and non metals.
ii. Groups- 18 Columns / 18 Groups
1. Elements in a column or group form a family.
2. Elements in a group have similar characteristics
b. Elements—classified by their properties, including melting temperature, density, hardness,
thermal and electrical conductivity.
i. Metals—most elements on periodic table
1. Found on left side and stretch to the right side of the table.
2. Physical Properties—
a. Thermal conductivity- ability of an element to transfer heat
b. Electrical conductivity-ability of an element to conduct an electric current
c. Luster- shiny and reflective
d. Malleable- can be hammered flat and rolled into sheets or other shapes.
e. Ductile—bendable and can be pulled out into long strands like wires.
f. Magnetic—can be made into magnets, are attracted to magnets
g. Solids at room temperature
i. Mercury (Hg) is a metal that is a liquid at room temperature.
3. Chemical Properties
a. Reactivity- the ease and speed with which an element combines with
another stubstance.
i. Metals react by losing electrons to other atoms.
1. Some metals are very reactive—Sodium (Na)
2. Some metals are not very reactive—Gold (Au)
a. All other metals reactivity fall somewhere in
between Sodium and Gold.
3. Corrosion—reactivity of a metal with air forming rust
4. Metals classified into several categories
a. Alkali Metals-Group 1
i. Most reactive metals on the periodic table
1. So reactive that they are never found in their “un-reacted”
uncombined states in nature. They are only found in
compounds that came from the reaction. Can only be
observed in their pure state in a lab.
ii. Soft and able to be cut with a plastic knife. Low density and low
melting point.
Ex- Francium (Fr) and Lithium (Li)
Potassium (K)
b. Alkaline Earth Metals- Group 2
i. Harder and denser with higher densities and melting points
ii. Very reactive but not as reactive as alkali metals.
iii. Never found uncombined in nature
Ex- Calcium (Ca)
c. Transition Metals- Groups 3-12
i. Hard and shiny solids:
Ex-Gold (Au), silver (Ag), copper (Cu), nickel (Ni), iron (Fe),
*mercury (Hg)
ii.
iii.
iv.
v.
High melting point, high density
Good conductors of heat and electricity
Very malleable
Less reactive than alkali and alkaline earth metals
**Still reactive but reaction takes a long period of time
d. Metals in Mixed Groups
i. Groups 13-16 contain many elements but only some are metals.
1. Aluminum (Al)-bright, shiny and light
2. Tin (Sn)—adds protection to steel to keep it from
corroding
3. Lead (Pb)—now used in car batteries. Used to be used in
pipes and paint but was found to be poisonous.
e. Lanthanides
i. Placed below and separate the rest of the elements of the
periodic table
ii. Top row—Lanthanides are special, and have different properties
than other elements. Neodymium (Nd) is found in compounds
that are used to make laser light for surgery, cutting metals, etc.
f. Actenides
i. Found under the lanthanides.
ii. These elements are NOT found in nature, but can be created in a
lab
1. Transuranium Elements OF ACTENIDE SERIES
a. Follow Uranium (U) in the periodic table.
b. Synthesized (made) when nuclear particles are
forced to crash into each other.
c. Called “synthetic elements”
i. Example Plutonium (Pu) is made in a
nuclear reactor.
d. Elements with atomic numbers over 95 such as
Curium (Cm), Einsteinium (Es) and others can only
be synthesized using a particle accelerator
i. Special machine that move atomic nuclei at
extremely high speeds
ii. When particles collide with a uranium
nucleus with so much force and speed they
them into a single new nucleus—A different
element is formed
iii. The higher the atomic number—the harder
it is to synthesize these elements.
5. Non Metals—have a wider variety of properties than metals.
a. Physical Properties
i. Found on the right side of the periodic table (except for Hydrogen
(H) which is the first element on the left)
ii. Poor conductors of electricity and heat
iii. Dull and brittle (not malleable)
iv. Lower densities than metals
v. Most are gases at room temperature—Oxygen (O), Hydrogen (H),
Helium (He), Nitrogen (N)
vi. Some are solid at room temperature—Carbon (C), Sulfur (S),
Iodine (I)
vii. Bromine (Br) only non metal that is a liquid at room temperature.
b. Chemical Properties
i. Share electrons very easily and form chemical bonds between
atoms, creating a molecule
c. Families of Non Metals
i. Carbon Family (Group 14)
1. In Group 14 Carbon is the only non metal
2. Very important
a. is found in every living thing on the earth
b. fossil fuels
c. diamonds
ii. Nitrogen Family (Group 15 has two non metals)
1. Nitrogen—makes up 78% of the Earth’s atmosphere and
not very reactive.
a. N2 is how nitrogen is found in nature
i. Diatomic molecule (2 atoms bonded
together)
ii. Most living things need nitrogen but cannot
use it until nitrogen fixing bacteria turn it
into compounds that we can use in a
process called nitrogen fixation
iii. Fertilizers add nitrogen to the soil
iv. Lightning coverts nitrogen gas in the
atmosphere into nitrogen compounds that
plants can use
2. Phosphorus
a. Much more reactive than nitrogen. Always found
in compounds in nature.
iii. Oxygen Family (Group 16 has three non metals)
1. Oxygen (O)- Gas at room temperature
a. Used by living things to breathe and get energy
from the food we eat.
b. Diatomic molecule (O2)
2. Sulfur (S) –Solid at room temperature
a. Rotten egg smell
b. Used in manufacturing rubber, car tires, rubber
bands
3. Selenium (Se)-Solid at room temperature
iv. Halogen Family (Group 17 has 4 non metals)
1. **Halogen means salt forming**
2. Very reactive and dangerous but very useful
a. Fluorine (Fl)
i. Most reactive of all elements
*Reacts with every known substance,
including water
*Flourine compounds are used in non-stick
cookware, toothpaste
b. Chlorine (Cl)
i. Very dangerous.
ii. Used to kill bacteria in water supplies
c. Bromine (Br)
d. Iodine (I)
i. Kills bacteria and disinfects
v. Noble Gases (Group 18)
1. Do not usually form compounds because they don’t gain,
lose or share electrons—NON REACTIVE
2. Helium (He) Neon (Ne) Argon (Ar) Krypton (Kr) Xenon (Xe)
a. Hot air balloons, party balloons, Neon signs, tube
shaped electric lights
vi. Hydrogen (Group 1)
1. Properties of hydrogen are different from all other
elements so it doesn’t fit in with a family
2. The most bountiful element in the universe (90%)
a. Stars are made mostly of hydrogen
b. Rarely found on earth as a pure element—but
found in large quantities as a comound H2O
6. Metalloids
a. Found between metals and non metals on periodic table
b. Share properties of both metals and non metals
c. All solids at room temperature
d. Brittle, hard, somewhat reactive
e. Great conductors of electricity
i. Depends on temperature, light exposure, etc.
ii. Used to make semi-conductors—substances that can conduct
electricity under certain conditions. * Computer chips, lasers
1. Silicon (Si) and Geranium (Ge)