Nuclear Chemistry

• In 1913 Niels’ Bohr, a Danish physicist proposed a new model for the hydrogen atom

•He proposed that the electron has certain orbits that it has to stay in that circle the nucleus

•The orbits can also be called ATOMIC ENERGY LEVELS

•An electron can move up from on level to a higher by absorption of energy

•An electron moves down a level by photon emission

•An electron in an atom can move from one energy level to another when the atom gains or loses energy

•In 1924 Louisde Broglie hypothesized that electrons have wavelike properties, as well as properties of particles, and they can be diffracted and can interfere with each other

•In 1927 Werner Heisenberg had an idea to detect electrons

-Electrons are detected by their interaction with photon and any attempt to locate an electron with a photon would knock the electrons off course because of the similar energy levels of the electron and photon

•It is impossible to determine, at the same time, the position and the velocity of an electron or any other particle

•In 1926 Erwin Schriodinger used the dual-wave particle nature to develop an equation that treated the electrons as waves

•Schriodinger’s work and the Heisenberg uncertainty principle laid the groundwork for quantum theory

•Quantum theory can be used to magmatically describe the wave properties of the electrons and other very small particles

•The electron cloud model replaced Bohr’s vision of electrons moving in predictable paths.

•Periodic table- a table where elements are organized by increasing atomic numbers (number of protons)

•1800s- Dmitri Mendeleev – first periodic table based on atomic mass – some elements were out of order or missing

•1913- Henry Moseley – arranged elements by atomic number – still used today

– Atomic numbers increase from left to right

•The table is organized in horizontal rows called periods

•From left to right, the properties of the elements change in a pattern

-Highly reactive metals, less-reactive, metalloids, and nonmetals

-This pattern os repeated in every period

•The elements fall into 18 column called groups (also called families)

•Contains elements with similar characteristics

•The periodic table has one square for every element

•Each square includes the elements

-Atomic number

•The number of protons and neutrons added together

-Chemical symbol

•An abbreviation of the name
-Element name

– Atomic mass

• Average of all the masses of the different forks of the element

• The number of protons in an element

•The number of protons is also equal to the number of electrons in a neutral species

•The mass number is the number of protons plus neutrons

•The same atom may occur with different numbers of neutrons (Isotope)

•The number of neutrons is the mass number minus the atomic number

•Ex: CI – 35 (mass) – 17 (atomic number) = 18 neutrons

•The periodic table is organized in order of increasing atomic number.

•Relative atomic mass is based on 1 atomic mass unit (AMU) being 1/12 the mass of a carbon – 12 atom.

•Amu – atomic mass unit, is 1/12 the of a carbon 12

•Average atomic mass – the weighted average of the naturally occurring isotopes

•Suppose the % abundance of copper – 63 (62.929amu) is 69.15% and copper – 65 (64.928amu) is 30.85%, what is the average atomic mass?

(0.6915 x 62.929) + (0.3085 x 64.928)

63.55amu

•The physical properties of metal include:
-Shininess
-Malleability
•A material that can be hammered or rolled into flat sheets or other shapes

-Ductility
•A material that can be pulled out, or drawn, into a long wire

-Conductivity
•A material that can transfer heat or electricity to another material

•The chemical properties of metals include:
-Reactivity
• The ease and speed with which an element combines or reacts, with other elements and compounds

-Corrosion
•The destructiveness of metal

•An element that lacks most of the properties of metal

•Most are poor conductors of electricity and heat and are reactive with other elements

•Soild nonmetals are dull and brittle

•Have some characteristics of metal sand nonmetals
-They are brittle, hard, and somewhat reactive

•Semiconductors
-Substances that conduct electricity under some conditions
-Most useful property

1)Alpha Decay
-Travels no more than a few centimeters in air and is stopped by a sheet of paper of clothing

2)Beta Decay
-Pass through paper, but can be stopped by a thin sheet of metal

3)Gamma Decay
-Takes several centimeters of lead or several meters of concrete to stop gamma radiation

•The time required for one-half of the nuclei of a radioactive isotope sample to decay to products

•After each half-life, half of the existing radioactive atoms have decayed into atoms of new elements

•What hold the nucleus of an atom together

•Binds neutrons and protons together in the nucleus

•The splitting of an atomic nucleus into two smaller parts

•Tremendous amounts of energy can be produced from very small amounts of mass

•E = mc2

•Process in which the nuclei of two atoms combine to form a larger nucleus

•Occurs on the sun to produce energy in form of light and heat