Atomic Number (Z) and Mass Number (A)

What is a neutron?

Match the atomic numbers 4,8,10,15 and 19 with the following:

Element with 6 valence electrons

 The mass number of an element is 18. It contains 7 electrons. What is the number of protons and neutrons in it? What is the atomic number of the element?

The atom of an element is made up of 4 protons, 5 neutrons and 4 electrons. What is its atomic number and mass number?

Name or state the following:

Elements having same mass number but different atomic number

Elements X, Y and Z have atomic numbers 6,9 and 12 respectively. Which one:

1. Forms an anion
2. Forms a cation

The diagram represents an isotope of hydrogen [H]. Answer the following:

Atomic no. = 1
Mass no. = 1

Are isotopes atoms of the same element or different elements.

Fill in the blank of the following statement :

All the mass of an atom is concentrated in a small region of space called the ___________.