Question

Draw the atomic structure of ${}_3{}^7\mathrm{Li}$ geometrically, clearly showing the (a) number of protons (b) number of neutrons and (c) number of electrons in various shells around nucleus .

Answer 1

• Atomic number is the number of protons of an atom.
• Mass number is the sum of the number of protons and neutrons of an atom.

a)Lithium atom has atomic number 3 (given as the subscript)

• Hence the number of protons=3

b)mass number=number of protons+number of neutrons

• thus the number of neutrons=mass number-number of protons
• mass number= 7
• the number of neutrons= (7-3) = 4.

c)An electrically neutral atom will have an equal number of electrons and protons.

• Electronic configuration is the arrangement of electrons in different energy levels around the nucleus of an atom.
• Hence number of electrons=3.
• electronic configuration:2,1.