Last seen: Jan 25, 2021
Mass of an atom is concentrated in nucleus.
Mass number = 27 ∴ p + n = 27 p = 13, (Atomic No. = Number of protons) ∴ 13 + n = 27 ∴ n = 14 ∴ Neutron =14
Atomic number = 12 ∴ Protons = Electrons = 12 Electrons Configuration = K L M -2 8 2 ∴ Valency = 2 Element is magnesium.
Electrons present in the outermost shell of an atom are called valence electrons.
Charge is +2 Mass is 4 a.m.u.
It has same number of protons and electrons, (positive charge = negative charge).
Because their outermost shell is completely filled.
Hydrogen atom 2s.png
(b) 2 positive charge and 4 mass unit
(c) 2, 8, 7
(d) all positive charge and mass of the atom is concentrated in small volume.
(c) protons and neutrons
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