Chemistry
Atomic number worksheet
INFORMATION
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 All atoms of the same element contain the same number of protons.
 The number of protons in a nucleus of an atom is called the atomic number (Z) of an
element (X). Elements in the periodic table are arranged in order of atomic number.
 The atomic number is also equal to the number of electrons found in an atom of an
element.
 The mass number (A) of an atom is defined as the total number of protons and neutrons.
Questions
1. Find ‘X’, ‘Z’ and ‘A’ for the following elements of the periodic table:
Element
Krypton
X
Z
A
Sodium
Fluorine
Lead
Oxygen
Nitrogen
Silver
2. Calculate the number of neutrons for each of the elements in Question One using the
values for A and Z.
Element
Number of Neutrons
(= A - Z)
Krypton
Sodium
Fluorine
Lead
Oxygen
Nitrogen
10SCI Term 2 Chemistry
1
Chemistry
Atomic number worksheet
Silver
3. Which element has 14 protons and 14 neutrons? Is it a metal, non metal or metalloid?
4. Which alkali metal has 20 neutrons?
5. Find the name of the element, and the number of protons for the following:
Symbol
‘X’
Element Name
Number of Protons
Li
Cl
Au
Ne
Ca
Hg
K
10SCI Term 2 Chemistry
2