Match the names of elements with their atomicity.- Iodine 8 Sulphur 4 Phosphorous 1 Sodium 2

Element name Atomicity Iodine 2 Sulphur 8 Phosphorous 4 Sodium 1 The number of atoms, present in a molecule of an element is known as atomicity. We can write formulas of elements by knowing the number of atoms in a molecule. For example atomicity of ozone is three.

Balance the following chemical equation. Mg + O 2 → MgO

Mg + O 2 → MgO Equations need to be balanced because of the law of conservation of mass. In this equation, magnesium atoms are the same on both sides of the equation but oxygen atoms are not the same. On the left side of the equation, a molecule of oxygen is present but on the right side, only one atom of oxygen is present. If we take two atoms of magnesium on the left side and balance it on right side, the number of oxygen atoms will be balanced as well. So, the balanced equation can be written as 2 Mg + O 2 → 2 MgO . In this equation number of atoms of each element participating is the same on both sides of the equation. Hence, the equation is balanced.

Balance the following chemical equation. N 2 + H 2 → NH 3

N 2 + H 2 → NH 3 Equations need to be balanced because of the law of conservation of mass. In this equation, there are 2 nitrogen atoms on the left side and 1 atom of nitrogen on the right side. So, nitrogen can be balanced by placing a coefficient of 2 on the right side before ammonia. Now, nitrogen atoms are equal on both sides. But hydrogen atoms become 6 on the right hand side and two on the left side. So, to balance put 3 as coefficient before hydrogen on the left side. So the equation can be written as N 2 + 3 H 2 → 2 NH 3 In the above equations, the number of nitrogen and hydrogen atoms are equal on both sides of the equation.

Balance the following chemical equation - SO 3 → SO 2 + O 2

SO 3 → SO 2 + O 2 Equations need to be balanced because of the law of conservation of mass. In this equation, the sulphur atoms are the same on both sides of the chemical equation. But there are 3 atoms of oxygen on the left side and 4 atoms on the right side of the equation. So, by placing the coefficient 2 before the sulphur trioxide on the left side of the equation, the number of an atom of oxygen becomes 6 on the left side of the equation, and 4 atoms of oxygen on the left side. Now place coefficient 2 before the sulphur dioxide on the right side of the equation. The equation can be written as 2 SO 3 → 2 SO 2 + O 2 The number atoms on the left side equal to the number of atoms on the right side, and the equation is balanced.