PS+2+-+Structure+and+Properties+of+Atoms


 * ====Standard PS-2:==== || ====[|The student will demonstrate an understanding of the structure and properties of atoms.]==== ||


 * Indicators:**
 * || PS-2.1 || [|Compare the subatomic particles (protons, neutrons, electrons) of an atom with regard to mass, location, and charge, and explain how these particles affect the properties of an atom (including identity, mass, volume, and reactivity).] ||
 * || PS-2.2 || [|Illustrate the fact that the atoms of elements exist as stable or unstable isotopes.] ||
 * || PS-2.3 || [|Explain the trends of the periodic table based on the elements' valence electrons and atomic numbers.] ||
 * || PS-2.4 || [|Use the atomic number and the mass number to calculate the number of protons, neutrons, and/or electrons for a given isotope of an element.] ||
 * || PS-2.5 || [|Predict the charge that a representative element will acquire according to the arrangement of electrons in its outer energy level.] ||
 * || PS-2.6 || [|Compare fission and fusion (including the basic processes and the fact that both fission and fusion convert a fraction of the mass of interacting particles into energy and release a great amount of energy).] ||
 * || PS-2.7 || [|Explain the consequences that the use of nuclear applications (including medical technologies, nuclear power plants, and nuclear weapons) can have.] ||
 * || PS-2.7 || [|Explain the consequences that the use of nuclear applications (including medical technologies, nuclear power plants, and nuclear weapons) can have.] ||

 • **__Atom__** - the smallest piece of matter that still retains the property of the element. • **__Nucleus__** - the small, positively charged center of the atom  •  The **__nucleus__** contains **__protons__** and **__neutrons__**. – **__Protons__** are particles that are positively charged. They have an electrical charge of 1+. – **__Neutrons__** are particles that do not have an electrical charge. – **__ Protons __** and **__neutrons__** have about the same mass • **__Electrons__** are particles with an electrical charge of 1-. • ** __Electrons__ ** have a much smaller mass than both **protons** and **neutrons** • **__ Protons __** and **__electrons__** have opposite charges so there is an attractive force between them. • **__Electron Cloud__** is the area around the nucleus of an atom where its electrons are most likely found.  –  The electron cloud is 100,000 times larger than the diameter of the nucleus. – ** Remember: ** electrons are constantly in motion.

• Elements are different because they have different numbers of **__protons__** – For example, every carbon atom has six protons • The **__atomic number__** is equal to the number of protons • The **__mass number__** of an atom is the sum of the number of protons and the number of neutrons – Mass number = protons + neutrons • mass # = protons + neutrons • # of protons = atomic # • # of neutrons = mass # - atomic # • **__Isotopes__** are atoms of the same element that have different numbers of neutrons. • The atomic mass of an element (as seen on the periodic table) is the weighted average of the masses of all the naturally occurring isotopes of an element.

•  Now the elements are put in rows by increasing **__ATOMIC NUMBER!!__** • The horizontal rows are called **__periods__** and are labeled from 1 to 7. • The vertical columns are called **__groups__** are labeled from 1 to 18.


 * Valence electrons are the electrons in the outer-most energy level of an atom.
 * Group || Family Name || # valence electrons ||
 * 1 || Alkali metals || 1 ||
 * 2 || Alkaline Earth metals || 2 ||
 * 13 || || 3 ||
 * 14 || || 4 ||
 * 15 || || 5 ||
 * 16 || Oxygen group || 6 ||
 * 17 || Halogens || 7 ||
 * 18 || Noble gases || 8 ||
 * 18 || Noble gases || 8 ||



• Nuclear reactions involve the particles in the nucleus of the atom. – Protons – Neutrons • There is a great deal more energy involved in nuclear reactions than in chemical reactions • Nuclear fission occurs when a neutron hits a heavy nucleus and it splits into two or more parts. • When the atom splits, a large amount of energy is released. • If one or more ejected neutron strikes another U-235 nucleus, another fission reaction may occur. The continuation of this process is called a chain reaction. • Critical mass is the amount of fissionable material required so that each fission reaction produces approximately one more fission reaction. • Fission is the type of nuclear reaction that occurs in nuclear power plants, and in other nuclear applications (weapons, submarines, etc.)

•   •  Nuclear fusion occurs when more than one light nuclei (such as hydrogen) fuse, or combine, to form a larger single nucleus (such as helium) • Just like in fission reactions, the mass of the products is less than the mass of the reactants • The ‘lost mass’ is converted to energy

[|Periodic Table Ineractive Tutoring]