Science(element in the Earth)?

Have a periodic table.
A periodic table consists of many squares, each representing a single element.
The Symbol of that element is written in the center of the square;
the Atomic number of the element is usually written on the top-left corner.

Atomic number of an element is the number of proton in an atom of that element.

Mass number of an atom is the SUM of number of proton & number of neutron in that atom.
In other words, number of neutron in an atom can be calculated by Mass number - Atomic number.

For a neutral atom, the number of electrons in that atom would be the Same as the number of proton, i.e. same as the Atomic number.


A is the 12th element.
No. of proton is the Atomic number;
Mass number can be calculated by summing no. of proton & no. of neutron;
no. of electron of an atom is equal to the Atomic number.

B has 17 electrons in an atom.
What is the number of proton in an atom?
What is the atomic number of B?
And no. of neutron = Mass number - Atomic number.

C is the 2nd element.
Mass number = ... + ...
no. of electron is equal to the number of ...