Ex1. an atom has atomic number z = 6 and mass number a = 12. establish:

a. what element it is;

b. how many protons, neutrons and electrons it has.

ex2. calculates the molar mass of hydrogen peroxide, h, 0, barium fluoride, baf, and carbon dioxide, co ,.

Ex1.

a) Carbon : atomic number Z = 6 and mass number A = 12

b) Protons = 6; electrons = 6 ; neutrons = 6.

Ex2.

Molar mass of H₂O₂ = 34 g;  BaF = 156 g; CO = 28 g.

Explanation:

Ex1.

a) the element with atomic number 6 and mass number 12 is carbon

b) number of protons and electrons in a element is given by its atomic number; and for neutrons its mass number - atomic number (A-Z).

⇒ protons = Z = 6;  electrons = Z = 6.;   neutrons = A-Z = 12-6 = 6.

Ex2.

Molecular formula of hydrogen peroxide is given by H₂O₂.

⇒ molar mass = 2×mass of hydrogen + 2×mass of oxygen

⇒ molar mass = 2×1 + 2×16 = 34.g

molar mass of BaF = mass of barium + mass of fluoride.

                               = 137 + 19 = 156 g

molar mass of CO = mass of carbon + mass of oxygen

                              = 12 + 16 = 28 g

found in the nucleus

has mass of one amu

trig 15.3 cos