Atomic Structure Flashcards
He was a Greek philosopher over 2000 yrs. ago. Believed there was a limit to dividing matter. Eventually you would reach the smallest piece and could no longer divide it without losing its identity. Democritus named the smallest piece of matter the atom. The word atom comes from the Greek word atomos meaning “un-cuttable”(a-tom).
Used only observations
Different atoms for every substance.
* He believed the world consisted of only two things: Atoms and the empty space around them.
* He was not believed because there was no proof and Aristotle did not believe in this.
Democritus (400 B.C.)
Used only observations
Different atoms for every substance.
* He believed the world consisted of only two things: Atoms and the empty space around them.
* He was not believed because there was no proof and Aristotle did not believe in this.
Democritus
Father of the modern atomic theory!
John Dalton (1800’s)
Dalton’s Atomic Theory
All elements are composed of atoms. Atoms are indivisible and indestructible particles
Atoms of the same element are exactly alike
Atoms of different elements are different
Compounds are formed by the joining of atoms of two or more elements.
He also proposed the first symbols for elements.
Cathode Ray Experiment Discovered Electrons (negative charge) Model was like a plum pudding. According to Thomson, the atom was made of a pudding-like positively charged material throughout which negatively charged electrons were scattered,like plums in pudding. Thus, “plum pudding model”.
J.J. Thomson (1900)
This great magician was born at the beginning of the fifth century BC, he first suggested that the world around us was made of elements - admittedly he only had four elements and spent the rest of his time as a magician.
- Earth, air, fire, and water
Empedocles of Acragas(490 - 430 BC)
Gold foil experiment
Discovered the nucleus (positive charge)
Model was like a solar system.
Also discovered alpha particles: positively charged particles emitted from certain radioactive substances.
Ernest Rutherford (1911)
Energy Level Model
The farther the energy level is from the nucleus, the greater the energy of the electron.
Adding energy moves an electron farther away from the nucleus. (Outer energy levels)
Energy is given off as an electron moves in.
Bohr (1913)
Wave Model
Very Complex
Electrons can be found anywhere in a certain region around the nucleus.
Model like the blades of a fan. (electrons are in all places at the same time)
DeBroglie
Uncertainty Principle.
Nothing can be observed in its natural shape because observing changes the very nature of things being observed.
You can not know the location and the velocity of an electron at the same time.
Heisenberg
Quantum Reality
Matter exists in all states except when being observed.
Can you travel across quantum realities?
Which one matters?
Schrodinger
Discovered neutrons
Scientist could not account for the density and mass of the nucleus on just the mass of a proton alone; in 1932, Sir James Chadwick did experiment similar to Rutherford’s and discovered the existence of neutrons.
Chadwick
Mass of a proton
approximately 1 amu
Mass of a neutron
approximately 1 amu
Charge of a proton
+1
Charge of a Neutron
0
Charge of an electron
-1
Mass of an electron
1/1836 amu
Considered to be negligible
If a water molecule were the size of a golf ball, a glass of water would be as big as
the Earth.
If a hydrogen nucleus was as big as a tennis ball, the electrons could be as far away as
.(from Cedar Shoals HS)
UGA
Is the same as the number of protons.
If you add or subtract protons, it is a NEW element.
In a neutral atom, # of protons = # of electrons.
Atomic Number
This = # of protons + # of neutrons. # of neutrons = This - # of protons
Mass Number
of neutrons = This - Atomic #
Mass Number
All atoms have neutrons except for
Hydrogen-1(protium).
Does the number of neutrons always equal the number of protons?
no
Atoms of the same element with different numbers of neutrons.
Atoms have the same atomic number but a different mass number.
These are indicated by writing the name of the element followed by a number; ex: Sodium-23 (has 11 protons and 12 neutrons.)
The mass of an atom in relation to carbon-12 is called the atomic mass.
Final atomic mass depends on these.
Isotopes
Exact location is somewhere in electron cloud.
Electrons
Exact location is somewhere in electron cloud.
Found at different energy levels
Electrons
Level 1: __ electrons
Level 2: __ electrons
Level 3: __ electrons
Level 4: __ electrons
2
8
18
32
Electrons that move from one level to another either_____ or _____ energy.
gain or lose
The abundance of a chemical element measures
how relatively common the element is, or how much of the element there is by comparison to all other elements.
number of protons
*Always a whole number.
Atomic Number
the number of protons and neutrons in an
isotope.
*Always a whole number.
Mass Number
mass of the atom of an isotope.
* Look this up in a book*
* Only Carbon-12 is a whole number
12. 00000amu
Atomic Mass
Number on the periodic table (in red). This number reflects the natural abundance of an element.
Atomic Weight
What shows the chemical symbol, the mass number and the atomic number of the isotope.
Standard nuclear notation
Dozen
12
Case
24
Gross
144
Three different ways to measure matter
counting
amount of matter
Volume
the SI unit that measures the “amount of substance”.
The Mole
This can be related to the number of particles, the mass, and the volume of an element or compound.
The unit mole
1 mole = how many representative particles of that substance.
6.02 x 10^23
There is exactly 1 mole of atoms in the atomic mass of an element when that mass is represented in
grams
6.02 x 1023 is an experimentally determined number called
Avogadro’s number
Avogadro’s number is the number of particles in exactly how much of a pure substance.
1 mol
Russian Chemist
Created first periodic table
Arranged atoms according to atomic mass
Left spaces for missing elements
Dmetri Mendeleev (1834-1907
British Physicist
Arranged the elements by order of atomic number
Basis of the modern periodic table is the Periodic Law
Henry Moseley (1887-1915)
Periodic Law:
When elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties.
Periodic Product:
One that repeats periodically. (example: coming of spring.) Properties of the elements are periodic.
The periodic table is arranged in groups (or families) and what
periods
Vertical columns
Similar chemical properties
Have the same number of electrons in their outer most energy level (valence electrons)
Groups/Families
Each horizontal row in the periodic table.
Have different chemical properties.
Have the same number of energy levels.
Periods
Classification of elements based on their properties. (3)
Metals
Non-metals
Metalloids
Occupy the left side and center of the periodic table. (Including the lanthanide and actinide series.)
3 or less outer electrons (valence electrons)
Shiny (luster)
Good Conductors of heat and electricity. (Au, Ag, & Cu are the most conductive metals)
All elements in groups 1 through 12 and some in 13, 14, 15 are metals.
Malleable—hammered into sheets
Ductile—stretched into wire
Have high tensile strength.
Metals
Occupy right side of periodic table.
Elements with 5 or more electrons in outer shell.
Dull and brittle
Do not conduct heat or electricity well. (insulator)
All elements in group 17 and 18 and some 13 through 16.
Nonmetals
Found along the heavy black zig-zag line on the right side of the periodic table.
Show some properties of metals and some properties of non-metals.
Elements that border heavy zig-zag line belong to this group. (Except Aluminum)
Metalloids
Extremely reactive
Never found in nature as elements.
React with water.
Low melting point.
Group 1: Alkali metals
Group 1
Alkali metals
Alkali Metals (group #)
1
Extremely reactive
Never found in nature as elements.
Group 2: Alkaline Earth metals
Group 2
Alkaline Earth metals
Alkaline Earth Metals (group #)
2
Groups 3-12:
Transition elements
Transition elements (group #s)
Groups 3-12
Group 13
Boron family
Group 14
Carbon Family
Group 15
Nitrogen Family
Group 16
Oxygen family
Group 17
Halogens (salt formers)
Group 18
Noble Gases (insert gases)
Electron Configuration
s, p, d, f orbitals
Moving left to right on the periodic table, the elements’ atomic size
decreases
Moving top to bottom on the periodic table the elements get larger because of
more electron shells.
Where are the smallest elements?
Upper Right
Where are the largest elements?
Lower Left
Atomic radius is measured in
angstroms
An _____ is 1/10 billionth of a meter.
angstrom
Amount of energy require to move a valence electron from an atom.
Tightly held electrons require a lot of energy to remove.
Upper right is the highest energy and lower left is the lowest energy.
A lone electron has low energy.
Ionization energy
A measure of the relative tendancy of an atom to attract electrons to itself when chemically combined with another atom.
Electronegativity
Ability to attract electrons.
High affinity and high ionization are nonmetals in the top right corner.
Lower left corner is low for both.
Electron Affinity
