Atom of chemical element consists of an atomic nucleus and an electron shell. Two types of particles - protons and neutrons are a part of an atomic nucleus. Almost all mass of atom is concentrated in a kernel because protons and neutrons it is much heavier than electrons.
It is required to you
- atomic number of an element, N-Z chart.
Instruction
1. Neutrons have no electric charge, that is their electric charge is equal to zero. It also represents the main complexity when determining number of neutrons - the atomic number of an element or its electron shell do not give definite answer to this question. For example, the carbon atomic nucleus always contains 6 protons, however protons in it can be 6 and 7. Types of kernels of chemical element with different quantity of neutrons in a kernel are called isotopes of this element. Isotopes can be natural, and can be and are received artificially.
2. Atomic nuclei designate by an alphabetic symbol of chemical element from Mendeleyev's table. To the right of a symbol above and below there are two numbers. The top number A is mass number of atom. A = Z+N where Z is a kernel charge (number of protons), and N is number of neutrons. The lower number is Z - a kernel charge. Such record gives information on quantity of neutrons in a kernel. It is obvious that it is equal to N = to A-Z.
3. At different isotopes of one chemical element number A changes that can be seen in record of this isotope. Certain isotopes have the original names. For example, the usual kernel of hydrogen has no neutrons and has one proton. Hydrogen isotope a deuterium has one neutron (A = 2, figure 2 from above, 1 from below), and isotope tritium - two neutrons (A = 3, figure 3 from above, 1 from below).
4. The dependence of number of neutrons on number of protons is reflected in so-called N-Z to the chart of atomic kernels. Stability of kernels depends on the relation of number of neutrons and number of protons. Kernels of easy nuclides are steadiest at N/Z = 1, that is at equality of quantity of neutrons and protons. With growth of mass number the area of stability moves to the sizes N/Z> 1, reaching the size N/Z ~ 1.5 for most heavy-nuclei.