Chapter 1.1:The Atoms and the Periodic Table Part 6 SABIS Grade 9 (Level K) Chemistry

Continue 

Atomic Number and Mass Number
The discovery of the proton eventually led to the realization that the number of protons in the nucleus of an atom determines its elemental identity. For example, an atom containing 80 protons is a mercury atom,an atom containing 8 protons is an oxygen atom, and an atom containing 29 protons is a copper atom.
Therefore, each element is defined by a unique atomic number, Z, which is the number of protons in an atom of that element. The atomic number for mercury is 80 because every mercury atom always has 80 protons. The atomic number for oxygen is 8, and the atomic number for copper is 29.The mass number, represented by the letter A, is the number of protons and neutrons in the nucleus of an atom of that element. For example, an oxygen atom with 8 protons and 8 neutrons has a mass number of 16; a copper atom with 29 protons and 34 neutrons has a mass number of 63.

In addition to having a unique atomic number, each element is represented by its own one- or two-letter chemical symbol. For example, hydrogen is represented with the single letter H and helium is represented with the two letters He. The first letter is always capitalized and the second letter, if used, is lowercase. These symbols provide a shorthand method for communicating chemical information.
The chemical symbol of an element is often combined with the mass number, A, and the atomic number, Z, as shown below, to represent the atomic symbol. Atomic symbols are used to communicate information about an atom:

As an example, the symbol   refers to a carbon atom with atomic number 6 and mass number 12. The atomic number indicates that the carbon atom has 6 protons and the mass number indicates that the carbon atom has 12 nucleons. Knowing the number of protons, you can find the number of neutrons by subtracting the atomic number from the mass number.
It is important to note that you can identify any element if you know either Z or X. This is because every element is defined by its unique number of protons. However, the number of neutrons can vary within atoms of the same element. For this reason, you can only determine the mass number, A, if you know the number of neutrons and either X or Z.
Fill in the blank.
The 
 is the number of protons in an atom of a particular element, and is used to identify the element.
Fill in the blank.
A 
 gives the number of protons and neutrons in an atom of an element, and gives information about the atom’s mass.
Fluorine (F) has 9 protons and 10 neutrons. The atomic symbol,  for fluorine is