Activity 3 1/10/11

What is an Atom?
      "An atom is a basic unit of matter that consists of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively protons and electrically neutral neutrons.The electrons of an atom are bound to the nucleus by the electromagnetic force." 
        The number of protons in a certain atom determines the chemical element and the number of neutrons determines the isotope of the element.
      An atom is the smallest component of an element having the chemical properties of an element.

What are the particles that make up an atom, list their mass and charge?
     The particles that make up an atom are protons, neutrons, and electrons. The atomic nucleus contains a mix of positively protons and electrically neutral neutrons. Electrons have a negative charge and are found on the orbitals that set stable energy levels.

What is the size of an atom?

     The atomic diameter can range from 62pm to 520pm. The radius of an atom varies with the location of an atom on the atomic chart, the type of chemical bond, the number of neighborin atoms, and a quantum mechanical property known as spin. An atom size tends to increase when moving down columns on the periodic table, but decrease when moving across rows (left to right).

What is the shape of an atom, where are the particles?
     Atoms exhibit a spherical shape; this is only obeyed for atoms in vacuum or free space.

What are the characteristics of electrons?

     Electrons are negatively charged and are located on the outer shell of an atom. They are bound to the nucleus by the electromagnetic force and set stable energy levels/orbitals and undergo transitions between them by absorbing or emitting photons that match the energy differences between the levels. Electrons determine the chemical properties of an element, and strongly influence an atom's magnetic properties.


http://en.wikipedia.org/wiki/Atom#Shape_and_size