Atom and molecule builder परमाणु और अणु निर्माता
Add protons, neutrons and electrons and watch the element, its isotope and its charge change. Then join atoms by their valency to make molecules and see how the electrons are shared or transferred.
Common questions
What decides which element an atom is?
The number of protons, called the atomic number Z. Changing the number of neutrons makes a different isotope of the same element; changing the number of electrons makes an ion.
How are electrons arranged in shells?
For the first 20 elements, NCERT uses the Bohr–Bury scheme: the K shell holds up to 2 electrons, the L shell 8, the M shell 8 (for these elements), and the rest go to the N shell. So sodium (Z = 11) is 2, 8, 1 and calcium (Z = 20) is 2, 8, 8, 2.
What is valency?
The combining capacity of an atom. If an atom has 1–4 outer electrons, its valency is usually that number (it loses or shares them); if it has 5–7, the valency is 8 minus that number (it gains or shares to complete an octet). Noble gases have valency 0.
What is the difference between ionic and covalent bonds?
In an ionic bond a metal atom transfers electrons to a non-metal atom, making oppositely charged ions that attract (NaCl, MgO). In a covalent bond non-metal atoms share pairs of electrons (H₂O, CH₄, CO₂).
Why is chlorine’s atomic mass 35.5 and not a whole number?
Natural chlorine is a mixture of two stable isotopes, chlorine-35 (about 3 parts) and chlorine-37 (about 1 part). The average mass is about 35.5 u.