atomic structure & periodic table introduction physical science jphancock
TRANSCRIPT
Atomic Structure & Periodic Table Introduction
Physical Science
JPHancock
The Atom
• Basic building block of all matter• Elements on periodic table are
represented as one neutral atom• Chemical symbols are abbreviated
ways of representing elements– C, H, N, O – Na, Cl, Ne, Cu– NaCl, H2O, CO2
Parts of the Atom
• Protons= (+) charge• Neutrons= (0) charge• Electrons= (-) charge• Quarks= smallest particles arranged in
groups of threes to make p+, e-, or n0
History of the Atomic Model
Aristotle 350BC
•Matter made up of earth, air, fire, and water
Democrit
us 400 BC
•Matter cannot be divided indefinately.
•“atomos = uncuttable”
Dalton
1803
•“Billard Ball Model” Atom solid and undivisible
Thomso
n 1904
•“Plum Pudding Model” – a (+)sphere with (-) particles embedded
Rutherford 1911
•Most of the mass in a (+) nucleus surrounded by (-) electrons
Bohr
1913
•(+) protons & neutral neutrons in nucleus
•e- are in shells and can jump to higher levels with energy
Rutherford Experiment
Electron Cloud Model-1926
• “Probability Cloud”• Electrons orbit the
nucleus in energy levels or orbits.
• Why is it considered a “probability cloud”?
EVOLUTION OF ATOM
PERIODIC TABLE
• The number of neutrons = mass number –atomic number
• In a neutral atom the number of e- and number of p+ are equal
• Every atom of the same element has the same number of protons
• MASS NUMBER =ATOMIC MASS
ISOTOPES
• Atoms of the same element with different numbers of neutrons
Atomic Mass Units• Do we now know how much atoms
really weigh, in pounds or grams?
• Yes, but we don't normally use those units for measuring the mass of an atom. It's much more convenient to use something called the atomic mass unit, or amu.
Using AMU is simplier!
• One gram is about 600,000,000,000,000,000,000,000 amu (that's 600 sextillion, or a 6 followed by 23 zeros). A pound is just shy of 300 septillion amu--that is, 300,000,000,000,000,000,000,000,000. (26 zeros there.)
Periodic Table
• 1869 Dmitri Mendeleev arranged the elements in order of their increasing atomic masses
• He discovered a pattern and was able to give rise to the modern
periodic table
Mendeleev’s Periodic Table
PERIODIC LAW
• The properties of elements are a periodic function of their atomic number– The properties change in a repeated
pattern as we move across or down the periodic table
– Elements are arranged by changes in physical and chemical properties
MODERN PERIODIC TABLE
• 1913 Henry G.J. Moseley• Arranged the periodic table based on
increasing atomic numbers
• PERIODS or Series –horizontal rows 1-7• GROUPS or Families-vertical columns
1-18 with similar properties
Properties of Groups
• Elements of same group have same # valence electrons– Valence electrons- are the e- in the
outermost energy level– Important role in chemical reactivity– Electrons closer to the nucleus have lower
energy than those farther away
Properties of Series
Ionization Energy
• Amount of energy needed to remove the outer electrons
• As you move right to left the radius of the nucleus increases meaning the size(distance) between the nucleus and electrons is greater
• As you move left to right the radius decreases meaning the electrons are valence electrons closer to the nucleus, held tighter and require more energy to remove
Atomic Radii
Electron Dot Diagrams
• Used to represent valence electrons in bonding