atomic structure & the periodic table
DESCRIPTION
Atomic Structure & the Periodic Table. Atoms. Atom. smallest particle that has the properties of an element. Democritus. PROPERTIES. Atoms are the building blocks of molecules. John Dalton’s Theory. every element is made of tiny, unique particles called atoms that cannot be subdivided. - PowerPoint PPT PresentationTRANSCRIPT
Atomic Structure & the Periodic
Table
AtomsAtom smallest particle that has the properties of an element
PROPERTIES
Democritus
Atoms are the building blocks of molecules
John Dalton’s Theory• every element is made of tiny, unique particles called atoms that cannot be subdivided• atoms of the same element are exactly alike• atoms of different elements can join to form molecules
What is an Atom?
Water
Three main Subatomic Particles
Nucleus the center of an atom; made up of protons & neutrons
Proton a positively charged subatomic particle in the nucleus of an atom
Neutron a neutral subatomic particle in the nucleus of an atom
Electron a tiny negatively charged subatomic particle moving around outside the nucleus of an atom
4 miles
Atoms have no overall charge?Atoms do not have a charge because they have an equal number
of protons & electrons whose charges exactly cancel.
Atomic ModelsBohr’s model
electrons in an atom move in set paths around the nucleus (like the planets orbiting the sun)
Energy level / shell any of the possible energies an electron may have in an atom
Atomic ModelsModern TheoryBohr’s model
It is impossible to determine both
the exact location of an electron (e- )
in an atom & its speed & direction
Visual method uses an… e- cloud
Shaded region used to demonstrate the possible location of an e-
Atomic Number Mass Number Isotopes
Model of Helium
What does an atom really look like?
The Electron Cloud Model is the current accepted model of the atom
This model illustrates the nucleus and the electrons in a cloud around the nucleus
Electron Orbitals• Electrons occupy the lowest energy levels available in an atom
• Within each energy level, e- occupy orbitals w/the lowest energy
• s, p, d, f – order of orbit strength (weakest to strongest)
Valence ElectronsValence electron Electron(s) in the outermost energy level of an atom
8e-
2e-
How do the structures of atoms differ?
Atomic number (Z) • the number of protons in the nucleus• Note: All atoms of the same element have the same atomic number/protons.• In a neutral atom the number of protons is equal to the number of electrons
Atomic Mass (A)
the total number of protons and neutrons in the nucleus of an atom
Because atomic masses are averages, many of them are decimals instead of whole #’s.
ISOTOPESDoes changing the number of neutrons affect the number of p+ & e- ?
Isotopes any atoms having the same number of protons but different numbers of neutrons
• have different mass #’s
Calculating neutrons
How many neutrons are in radioactive uranium-235?
Mass of an Atomatomic mass unit (amu) a quantity equal to one-twelfth of the mass
of a carbon-12 atom
average atomic mass the weighted average of the masses of all naturally occurring isotopes of an element
EX: Determine each of the following given this picture…
# e-
# p +
# n
Atomic #
Mass #
Element Name
Element Symbol
Now Complete the handout “I/S Atomic Structure Worksheet”…
Then, let’s go over the intro packet (first couple of pages…).
IONSAtoms of Group 1 elements are reactive, why?
• because their outermost energy levels are only partially filled
Ionization process of adding e- to or removing e- from an atom or group of atoms
Ion an atom or group of atoms that has lost or gained one or more e- and therefore has a net electric charge
Cation an ion w/a positive charge
Li Li ++
IONSAnion an ion w/a negative
charge
F F --
How do the structures of atoms differ?
Atomic number (Z) the number of protons in the nucleus
Mass number (A)the total number of protons and neutrons in the nucleus of an atom
Periodic Table• elements are represented by their symbols
• arranged by # of protons found in the nucleus
Periodic Law properties of elements tend to change in a regular pattern when elements are arranged in order of increasing atomic # (# of protons in their atoms)
Periodic TableDmitri Mendeleev
?
Mendeleev arranged the elements into rows in order of increasing mass so that elements w/similar
properties were in the same column
Why couldn’t Mendeleev make a complete periodic table?
Gallium
Periodic Table
Group (family)
a vertical column of elements in the periodic table
Period a horizontal row of elements in the periodic table
• the # of p+ & e- increase by one, moving from left to right
• group members have the same # of valence e-
• have similar properties
Element Families• elements are classified as either metals or nonmetals
Metals the elements that are good conductors of heat & electricity
Nonmetals the elements that are usually poor conductors of heat & electricity
Semiconductors the elements that are intermediate conductors of heat & electricity
Metals (4 types)
Alkali metals highly reactive metallic elements located in Group 1 of the periodic table
Are alkali metals often found in nature as
elements?
Alkaline-earth metals reactive metallic elements located in Group 2 of the periodic table
MetalsTransition metals metallic elements located
in Groups 3-12 of the periodic table
radioactive nuclei of the atoms are continually decaying to produce different elements
Nonmetals• include some elements in Groups 13-16 & all in Groups 17-18
Carbon is usually found as what, in its’ pure state?
NonmetalsThe most plentiful gases in the air are…
N & O Odorless yellow solid?
Halogens highly reactive elements located in Group 17 of the periodic table
Poisonous Poisonous yellow-green gas?yellow-green gas?
Cl is widely used to kill bacteria
NonmetalsI is used in table salt to prevent goiters from forming (enlarged thyroid gland)
Fl is used in some toothpastes & added to drinking water to help prevent tooth decay
Noble Gases unreactive gaseous elements located in Group 18 of the periodic table
Ne is responsible for…
Why are the noble gases so unreactive?
He is lighter than air & gives balloons lift
Ar prevents filaments from burning
Semiconductors Semiconductors (metalloids)
nonmetals exhibiting some metallic properties under certain circumstances
Silicon is the most familiar semiconductor, making up 28% of the earth’s crust
Electron OrbitalsOrbital a region in an atom where there is a high probability of
finding electrons
Four Orbital Types
Simplest…sshaped like a sphere
max 2 e-
pdumbbell-shaped
max 2 e-
/orbital (3)
max 2 e-
/orbital (5)
max 2 e- /orbital (7)
d
f
Energy Levels, Orbitals, and Electrons Energy Level # of Orbitals Max # of Electrons
1 1 2
2 4 8
3 9 18
4 16 32
Electron Orbitals
Question?
Atoms are mostly________?
A. Protons
B. Neutrons
C. Electrons
D. All of these
E. None of these
Answer
E. None of these
Atoms are 99.999% empty space, essentially a vacuum.
There is the nucleus and the electrons circling around it
Between the nucleus and circling electrons there is absolutely nothing!
The nucleus makes up 99.9% of the atom’s mass.
Facts
The radius of the electron cloud is 10,000 times larger than the nucleus of the atom
Even with this huge cloud, it contains almost none of the total mass of an atom
The volume of an atom is 1 trillion times larger than the nucleus